Since they can seem confusing to those unfamiliar with the arcane hieroglyphs,
here is a primer of C. F. Martin & Co. Model Designation
The Model Name – two sides of a dash
There are two halves to a typical Martin model designation, with the name separated by a dash.
The first half refers to the “size” or physical dimensions of the guitar, and the second half refers to the visual appearance of the instrument and the materials used to create it, known as the instrument “style.”
REVISED: July 21, 2017
*Note: that statement and what follows does not include the designation “14”, as in D-14, 00-14.
This is a modern invention to denote a 14-fret guitar that a Martin dealer ordered with custom specifications in size D, 00, et al. SEE BELOW*
The body size was originally designated as a number. In staying with customary sizing used by toolmakers and woodworkers, the higher the number on the left side of the dash, the smaller the size of a Martin guitar. Some later models use letters for their size indicator.
C. F. Martin Sr. founded his business in 1833 and was soon offering guitars in sizes ranging from a tiny size 5 on up to a size 1 (that still seems amazingly small by modern standards.)
So when they needed a larger size, Martin used Size 0. It was considered large enough for a public concert.
As guitarists began to perform in larger halls, alongside banjos and the mandolin, C. F. Martin Jr. offered the 00 in 1873, the same year C. F. Sr. passed away. It was deemed an extra-large guitar for “grand concerts.”
The 000 followed shortly after 1910. It was looked upon as enormous at the time. All of these sizes were originally traditional 12-fret neck designs, typically employing gut strings.
Be they 12 or 14-fret guitars, the most common Martins of the twentieth century can be equated thus:
0 = Concert, 00 = Grand Concert, 000 = Auditorium, 0000 = Grand Auditorium (aka size M,)
OM = shares the same body size as a 000, but typically has other differences.
D = Dreadnought (similar to Gibson’s Jumbo size), J = Jumbo (similar to Gibson’s Super Jumbo size)
Arriving after year 2000 were the Grand J = Grand Jumbo (similar to Guild’s Jumbo,) GP = Grand Performance (similar to Taylor’s Size 14 and the “Small Jumbo” size of many other makers,) and 00L = a 14-fret 00 with Long silhouette due to its “slope shoulders” similar to a 12-fret Martin. They were inspired by the Gibson size L guitars, but retain the same depth as other Martin oo and ooo guitars.
Other builders of guitars have adopted terms like OM and Grand Concert for generic use since the 1970s, typically indicating a 14-fret instrument with a smaller size and narrower waist than the Dreadnought or Jumbo body shapes.
As stated above, “grand concert” originated with Martin’s 12-fret body size of the 1870s. But in its original definition, OM for Orchestra Model actually meant a 14-fret steel string Martin, as opposed to their 12-fret guitars originally designed for gut strings. Initially, the original 14-fret Martins, invented in 1929, were made in the Auditorium size only and given model stamps like OM-18, OM-28. The stamp and model names were changed back to 000 when Martin converted all their sizes to 14-fret orchestra models in 1934. See below for the differences between modern 14-fret 000s and OMs.
The instrument Style is also represented by a number. With few exceptions, the higher the style number, the fancier and more expensive the materials and appointments.
Typical examples of model names include: 000-18, D-28, OM-45.
A 000-18 stands for Size “Triple Oh” (or at the Martin factory, “Triple Naught”) in Style 18, which includes mahogany back and sides, and a top of spruce, with dark bindings on the body, an unbound neck and white dots on the fingerboard, etc.
A D-28 stands for a Dreadnought body in Style 28, which includes rosewood for the back sides, a spruce top, white binding and typically ebony for the fret board and bridge, etc.
An OM-45 is an Orchestra Model size in Style 45, the top of the line for a basic catalog model, which includes top grade rosewood with abalone shell inlaid along the edge of the spruce top, as well as every edge along the back and sides, in addition to fancy, abalone fret markers, a bound neck etc.
In modern times additional indicators have been added onto some model names.
i.e. 000-18GE 1937, HD-28VS, GPC-42E. These translate to:
000-18GE 1937 – 000 size in Style 18, with specs designated for the Golden Era Series of vintage reissues, in this case based upon the 000-18 made in 1937.
HD-28VS – Dreadnought size with Herringbone trim around the edge, in Style 28 with specs of the Vintage Series, using the 12-fret version originally known as the Standard body design. Guitars with Herringbone trim usually come with scalloped braces. Examples include HD-28, HD-35, 000-28H.
GPC-42E – Grand Performance size with a Cutaway body, in Style 42 with a built-in Electronic amplification system.
*As mentioned above, “14” when appearing in shops or on line as in D-14, 000-14, etc. does not denote the guitars “style.” Quite the opposite, since it does not give any indication of what wood or non-wood materials were used to build the instrument, what sort of neck joint, neck block, bracing, finish, the instrument has, as would an actual Martin style designation like 18, 28, 45, etc.
It is not unheard of for some merchants to order customized Martin guitars based on various lower-level Series not represented in this article, which are dressed up to appear like higher-end models, and then price them beyond their merits when it comes to what is under the hood, as it were.
When shopping for Martin guitars and you see something listed as a D-14, or OM-14, ask the dealer what was the base model or “starter model” for the custom guitar in question, which will tell you a lot more about the level of quality and construction than may be obviously apparent.*
TABLE: Common Styles and How They Vary Based on the Series
Note: Style 18 has mahogany back and sides, all others listed below have rosewood back and sides. All styles have 100% solid tone woods throughout.
|Style||Standard Series||Vintage Series||GE/Marquis Series|
|18||Style 18 in 2016 has genuine Big Leaf Mahogany back and sides, Sitka spruce soundboard and bracing, ebony fingerboard and bridge, mother of pearl fingerboard dot markers, open-backed tuners, tortoise colored binding and pickguard, aging top toner, with an overall appearance reminiscent of Style 18 from the late 1930s.
D-18, D-18E (intro. 7/17,) DC-18E, GPC-18E, GP-18E (intro. 7/17) have forward shifted, scalloped 5/16″ braces. 0-18, 00-18, 000-18 and OMC-18E, OM-18E (intro. 7/17) have scalloped 1/4″ braces.
All Style 18 Martins now have the High Performance neck (Modified Low Oval Profile, High Performance Taper, 1-3/4″ width at nut and 2-1/8″ at the 12th fret, with 2-5/32″ string spacing.)
Previous Style 18:
Rosewood was used for the fingerboard and bridge from 1940s until the recent return to ebony. Pickguard and binding was black plastic between 1966 until the same makeover, when it returned to tortoise.
Non-scalloped bracing on D-18 and 000-18, each having a 1-11/16″ neck from 1939 to recent makeover.
|The D-18V and OM-18V are now retired, but still common on the used market. They have a Modified V neck profile (the D has a 1-11/16″ width at nut and 2-1/8″ string spacing, the OM has 1-3/4″ width at nut and 2-3/8″ string spacing.
The modern Standard D-18 has many features of the D-18V, but with the modern High Performance neck.
|Example: D-18 Golden Era
Add Adirondack spruce top, 1-3/4” Modified V neck with ’30s Style heel (tubbier overall feel,) upgraded tuners, wood fiber inlays instead of plastic, etc.
Golden Era scalloped bracing has more wood removed compared to Standard/Vintage Series bracing, leading to more flexibility and resonance at a lighter attack.
18GE had Brazilian rosewood accents 18 Marquis had Madagascar rosewood accents.
|21||2016 – Limited to OM-21 model, includes scalloped 1/4″ braces, High Performance neck.
Indian rosewood back and sides, Sitka spruce top, ebony fingerboard and bridge, short-pattern diamond fret markers – single at 5, double at 7, single at 9 – no purfling on edge of top, side, or back, Style 18 back strip.
Previous Style 21 1990s – 2012: Indian rosewood bridge and fingerboard with white microdot fret markers, tortoise binding and pick guard. No top purfling or back strip.
Old Style 21 was discontinued in 1969. Originally, it had a herringbone rosette, discontinued in the 1940s, when it became, basically, Style 18 with rosewood for the back and sides instead of mahogany, and usually rosewood with grain that was not straight and traditional enough to use on Style 28.
|21 Special||Limited to OM-21 Special and D-21 Special.
Add many cosmetic features of Style 21 circa 1905, but otherwise a Standard Series OM and Dreadnought model, but made with Spanish cedar necks, which lightens up the weight of the guitar and contributes to a more open, airy sound.
Also, they have a 1-3/4″ low profile neck and 2-5/16 string spacing.
(Both models now discontinued but frequently on the used market.)
|28||Indian Rosewood back and sides (Brazilian rosewood until 1969.)
Ebony fingerboard and bridge. White mother-of-pearl dot markers. White binding.
D-28, D-28S (discontinued,) GPC-28E, GP-28E (intro. 7/17) have 5/16″ non-scalloped braces. OM-28 and OMC-28E have 1/4″ scalloped braces.
HD-28 gets herringbone top trim, scalloped 5/16″ braces, and tortoise colored pickguard.
D-28 received a makeover as of July 2017. It now has the modern High Performance neck, and forward-shifted non-scalloped bracing.
HD-28 has 1-11/16″ low profile neck with 2-1/8″ string spacing.
OM-28 and all 28E models have the High Performance neck.
OM-28 absorbed many features from the retired OM-28V including herringbone top trim, diamond and squares fingerboard markers, tortoise pickguard and grained ivoroid binding.
My sources suggest that all Standard Style 28 guitars will switch to the styling of the New D-28, eventually. This includes Aging toner, black and white ply purfling, Antique white binding, High Performance Neck, faux tortoise pick guard, white MoP dot fret markers.
|Higher grade Sitka spruce, add diamond fingerboard markers, grained ivoroid binding and tortoise pick guard, herringbone trim, forward-shifted scalloped braces. Modified V neck, with 2-5/16″ string spacing, etc.||Add Adirondack spruce top, 1-3/4” V neck with ’30s heel (tubbier feel overall,) wood fiber inlays instead of plastic, forward-shifted, Golden Era bracing (see Style 18 above.)
|35||Indian rosewood back and sides. (Brazilian rosewood to 1969.)
Three-piece back, Sitka spruce top and braces, ebony fingerboard and bridge, white mother-of-pearl dot markers, white binding, black pick guard.
D-35, D-35S (discontinued,) DC-35E, GPC-35E. GP-35E (intro. 7/17) have 1/4″ non-scalloped braces.
OM-35E (intro. 7/17) OMC-35E (intro. 1/17) and HD-35 have scalloped braces.
HD-35 has herringbone top trim, tortoise pickguard and grained ivoroid body.
Style 35 first appeared in 1965 and had tortoise binding and pickguard.
“35” has appeared in the model name of several special or limited editions, with woods or appointments different from above. The defining 35 features being a three-piece back and a bound fingerboard.
|41||Higher grade Indian Rosewood and Sitka spruce than 28 or 35. Abalone shell trim around top and rosette, but not the fingerboard extension on the top. Abalone hex inlays on neck, etc. Scalloped braces.
Original D-41 had non-scalloped bracing, earliest examples have Brazilian rosewood back and sides (1969.)
Style 41 Special – Vintage Style 45 snowflake fingerboard, grained ivoroid binding, forward-shifted braces (Size D and Size J) and Modified V neck (1-3/4″ on Size 000.)
|42||Highest grade Indian Rosewood and Sitka spruce. Grained ivoroid bindings, Abalone trim on top, including fingerboard extension, Vintage Style 45 snowflake inlays on fingerboard and bridge, Scalloped braces, forward shifted on D-42.||N/A||Only 000-42 Marquis (discontinued.) Add highest grade Adirondack spruce top, 1-3/4” Modified V neck with ’30s heel, wood fiber purfling around the pearl trim instead of plastic, etc. Short snowflake pattern on fingerboard, ¼” scalloped braces.
Vintage Style 42 can be seen on the 2016 000-42 Authentic 1939 with usual Authentic specs (hide glue construction, VTS torrefied Adirondack top, etc.)
|45||Highest grade Indian rosewood and Sitka spruce. Abalone trim on all edges of top, sides and back, hex inlays on neck, etc. Scalloped braces.
Earliest modern examples (1968-69) had Brazilian rosewood and European Alpine spruce tops.
Black pickguard replaced with tortoise in recent years.
|Add Modified V neck, Snowflake fingerboard pattern, grained ivoroid bindings, vintage top toner, tortoise pick guard, forward-shifted scalloped braces.||Add highest grade Adirondack spruce top, 1-3/4” Modified V neck with ’30s style heel, wood fiber purfling around the pearl trim instead of plastic, Golden Era bracing (see Style 18 above.)|
Note: specs listed are only notable examples.
* Authentic Series not included in this table. Each Authentic model is as as-close-as-possible recreation of a specific Martin guitar from a specific year. Examples include D-18 Authentic 1939, OM-28 Authentic 1931, 00-18 Authentic 1931. See more specific reviews HERE.
** The Golden Era Series was introduced after the Vintage Series, to offer more-accurate vintage reissues, which included the use of Adirondack spruce and also Brazilian rosewood as back and sides on Styles 28GE and 45GE and for cosmetic trim on Style 18GE guitars. Prior to the official series getting under way, a version of the D-18GE was made with a Sitka spruce top, as was a 12-fret 000-28GE.
The Marquis Series was introduced after the shortages of Brazilian rosewood halted GE production. Marquis guitars are basically identical to GE models, except for the substitution of Brazilian rosewood with Indian rosewood on 28 Marquis and 45 Marquis, as well as Madagascar rosewood as trim on 18 Marquis. Some additional, minor changes occurred over time, like the brand of tuning machines, etc.
Surviving members of the Vintage Series, Golden Era Series, Marquis Series, are currently found with the Authentic Series under the umbrella of Martin’s “Marquis Collection.”
Just the Facts
Q: Why are there many numbers missing among the Martin Style names?
A: Some styles have gone extinct. The earliest Martins were made in a variety of sizes and cosmetic trim. At one point, Mr. Martin matched one body size with one style of trim. Each was assigned a specific price. A guitar in Size 1 cost $17 and became known as Style 17.
Once prices began to rise, the original Style names stuck, but were associated with the specific trim rather than the price. These set trim styles eventually began to appear on different sizes. Old C. F. died in 1873 but his son and grandsons continued to use and expand upon his methods. By 1900 the current system of Size on one side of the dash and Style on the other was well in place.
Some Style numbers that were gone by 1950 have been resurrected, but with cosmetic specs or woods that are different from their original version.
Example: Style 17
Style 17 had Brazilian rosewood back and sides and a spruce top in the 1800s. It was changed to mahogany back and sides circa 1906 and was retired in 1918, when Style 18 was switched from rosewood to mahogany.
Style 17 was reborn in 1922, in all mahogany (including the top,) with a satin finish (similar to today’s Style 15, which only existed as the 0-15 with a spruce top until 1940, when it was given a mahogany top.)
Style 17 was made in smaller and smaller numbers until retired in 1961 (with a one year resurrection in 1967.)
It returned again as a fancier version of modern Style 15, with white purfling and a high-gloss finish, before being put to bed yet again.
More recently, Style 17 was revived as basically a 15 Series guitar with a spruce top instead of mahogany, and with a reddish finish tint and sunburst top in a 14-fret Dreadnought size and a 12-fret 000, the 000-17S. Those have since been retired.
In 2016 three new sizes were offered in Style 17 (the 12-fret 00, 14-fret 00L, and 14-fret 000), with two new cosmetic packages, the Black Smoke (all black with white trim and pickguard) and Whisky Sunset (bronze-orange to black sunburst.) And Style 17 is now re-positioned as Depression Era budget guitars made of all solid wood for players looking for a great value with a spruce top.
More details about Martin model designations
When compared to current designs, Martins prior to 1930 were similar to modern, Classical guitars in many respects, all having an elongated shape with a wide 1-7/8″ neck that offered only 12 frets clear from the body and top braces intended for gut strings. In fact, Martins were the preferred choice for American concert professionals performing the classical repertoire in the decades between the Civil War and the Second World War.
Martins moved into a position of prominence in popular, country, and folk music once their 14-fret steel string guitars appeared during the Great Depression. Andre Segovia’s tours of the US during the 1930s and ’40s shifted Classical guitar firmly toward guitars that evolved in Spain at the same time Martins were evolving in America.
Martin shifted their own focus toward steel strings during the early twentieth century, but other than their Hawaiian-style guitars meant for playing with a steel slide, they did not design guitars specifically for steel strings until the OM, which first appeared in the 1930 catalog.
The Orchestra Model was the first Martin guitar to break with the numbered size convention, when its model stamp on the neck block was represented by the initials: OM. It was designed with a longer, 14-fret neck and a body braced exclusively for steel strings, and it was named to attract dance orchestra banjoists, who were converting to guitars once steel strings became the norm.
Although some Jazz musicians played the new steel string Martins, it was actually pop music icons like Gene Autry and Roy Rodgers, singing in front of bands on the new sensation of radio, who embraced the revolutionary new design. In later years it was traditional Blues soloists, and eventually New Age fingerstyle guitarists who took the OM into ever expanding genre of guitar music.
Because the OM and the 14-fret 000 share the same body size, there is often confusion about how their modern examples differ and why. (See below for more information about that.)
D – Dreadnought
Other model names without numbers include D for Dreadnought. These are the large, now iconic guitar shapes that Martin invented in a 12-fret size in 1916, exclusively for the Ditson musical department store chain, which intended them to be used as the “bass guitar” in mandolin orchestras.
Dwarfing all other sizes at the time, Dreadnoughts were named after the British battleship H.M.S. Dreadnaught (sic), but also as an insider joke. Their largest sizes were the Naught, Double Naught and Triple Naught. This new size was the biggest Naught of them all.
Martin put out a dreadnought under their own brand in 1931, and three years later, a 14-fret version was released as well, which became the most popular steel-string guitar design in history. For example, the memorable acoustic guitars played by Johnny Cash, Neil Young, Nirvana’s Kurt Cobain, and Coldplay’s Chris Martin are Martin dreadnoughts.
M or 0000 – Grand AuditoriuM
The M size was introduced in the 1970s. It stood for Grand Auditorium and at times is referred to as the 0000, or Quadruple Oh/Naught. It is a flattop guitar that uses a body shape taken from the mold of a Martin archtop model made during the Jazz Age. They actually used the molds from the 1930s to make the sides.
At its introduction, the M had the widest Martin top, matched with sides having the depth of an OM. Ms are known for their even balance, sounding similar to the Dreadnought with the bass pulled back in line with the other registers.
J – Jumbo
The Martin Jumbo was the brainchild of C. F. Martin IV, the current CEO. It has the top size of the M but the depth of the Dreadnought. To my ear it sounds like a super-sized 000, with balance across the registers, but with considerable volume, and a focused, punchy midrange.
GJ – Grand Jumbo
Like the M, the Grand J takes its body from an archtop, only this time it was Martin’s modern Jazz guitar, the CF-1. But after some prototype examples, they altered the exact shape a bit. It has a 17” wide lower bout, the widest flat top Martin has ever made. The Grand Jumbo has only been around a few years. It has appeared as normal 6-string and 12-string models. But it has also been used on limited edition baritone models, designed with a longer neck for lower tunings.
GP – Grand Performance
The company’s first totally new flat top body size in many decades. With a top slightly wider and rounder than an OM and a deeper body, they are Martin’s version of the “small jumbo” models that have grown in popularity in recent years. While Gibson’s J-185 from the 1950s might be considered the first true small jumbo, it was in the 1980s that indie luthiers Kevin Ryan created the design associated with the term today, while a similar design by James Olson was most responsible for small jumbo’s surge in popularity among professional artists. But Taylor’s Size 14 design is what got it into the hands of the common guitar player. And Martin’s GP with a cutaway is almost identical to the Taylor design in terms of dimensions. In general, they sound like an OM with a more pronounced bottom end and with greater volume.
00L – Slope Shoulder Grand Concert
The 00L (L for Long) size debuted in 2014 with the CEO-7, which was designed by C. F. Martin IV as a nod to Gibson’s fabled L00 guitars of the 1930s. After a couple of limited edition CEO models that combined Martin’s original slope shoulder dreadnought shape with a 14-fret neck, he decided to put the longer slope shoulder shape on a 14-fret 00, creating a smallish guitar with a slightly larger sound chamber than the normal 00, increasing the bass response. It was a sensational success. The more affordable 00L-17 followed in 2016.
Now back to the OM – 000 confusion…
To make the revolutionary OM, Martin turned to their Standard 12-fret 000, which was the largest size they offered in 1929. Basically, they squashed the slope shoulders down almost flat, which exposed two more frets and pushed the upper bout farther out. This also had the effect of placing the bridge closer to the neck relative to the overall body length.
Then they narrowed the neck from 1-7/8″ to 1-3/4″ for the target audience of banjoists and added bracing designed to work best with the tensions of steel strings … and viola! They invented the modern, flat top acoustic guitar.
After three years, it was clear Martin was going to convert the bulk of their catalog to the new 14-fret steel string design, so the OM stamp was replaced with 000, sometime in the early months of 1934. This allowed them to get back to their traditional numbered sizes, while offering each size in a 12-fret and 14-fret version.
At Martin, at least, any guitar made from that point on with the 14-fret design was an “Orchestra Model.” In fact, during the first years that the 14-fret dreadnought was offered in the Martin catalog, it was listed as “Orchestra Model, Size-D”.
Guitars that retained the elongated body and 12-fret neck were referred to as Standard models and in modern times an S is added to their neck block stamp for “Standard”, sometimes confused with guitars made up through the 1950s that had an S added for “Special”, typically meaning some sort of customized Martin before they had an official custom order policy.
The 14-fret 000s made in the first months of 1934 are identical to the OMs made in 1933. But soon after, changes were instigated in the design, as the tension from steel strings was causing too many repair issues. The first major change was having the string scale shortened by half an inch, equal to that on 14-fret 0s and 00s. The new, short-scale 000s also has their tone bar braces increased from 1/4″ to 5/16″. It remains a question of history as to exactly which came first, the change to 5/16″ tone bars, or the short-scale neck, or if they arrived at the same time.
All 14-fret Martins went to a narrower 1-11/16″ neck in 1939 and the company stopped using scalloped bracing in 1944 (Actually this was transitional, as 1945 Martins have what is now called tapered bracing.)
So, by the mid-40s the 14-fret 000 had an auditorium body size, a short-scale neck equal to smaller Martins, but bracing of the size and density found on the larger dreadnoughts.
The Martin 000s of the 1950s and 60s continued this overall design, as they stood up well to thick flat picks and steel fingerpicks popular at that time, and fit into ensemble playing, as the guitars’ punchy notes could cut through a group without upstaging other instruments.
The Modern OMs
Starting in 1969 Martin answered the call for guitars made in the tradition of the original OM-stamped guitars, with sporadic special editions. The “OM” became an official model type in 1990, which has the same shape as the 14-fret 000. But otherwise, several differences separate the two designs.
The traditional 14-fret 000 had evolved to have a narrow, short-scale neck and 5/16” non-scalloped bracing.
Modern OMs have a wider, long-scale neck and 1/4″ scalloped bracing. (The OMs made in the 1930s actually had a center X-brace that was 5/16”, surrounded by 1/4″ tone bars.)
Because of all the vintage reissue models and limited editions that have come out in the past 25 years, the lines between 000s and OMs have blurred.
Traditional 000 necks have the short scale, while 000s below Style 18 have a long-scale neck, since that is now the industry standard. But the new 2016 000-17 has returned to the short scale and acquired the modern High Performance neck. Martins shall ever and always continue to evolve.
Vintage-style 000s often have a 1-3/4” neck, like the Eric Clapton models and the 000-42. And those in the Marquis/GE series also have 1/4″ OM-style bracing to help make them sound like the lighter, more resonant 000s from the 1930s. This is because modern guitars are made with thicker wood and finishes to withstand the rigors required of a lifetime warranty.
Some Limited Edition/Custom Artist OMs, like the John Mayer and Paul Simon models have necks narrower than 1-3/4” and so on.
To confuse matters more, many OMs and 000s have been converted to the modern High Performance neck. It has a 1-3/4″ width at nut, but the overall neck is closer in width and string spacing to a traditional 1-11/16″ Martin neck. It is just cheated a bit wider down in the “cowboy chords” area below the 5th fret.
Despite the many exceptions, it is safe to say that typical Martin OMs have lighter, scalloped bracing matched with a long-scale neck that has a 1-3/4” width at nut. Any other defining characteristics depend greatly on the specific year or era of construction.
OMs are recognized today by their small, roundish pick guard, even though the original OMs from the 1930s switched to the longer Martin pick guard about six months into production.
How do they sound? To my ear a typical 000, with 5/16” bracing, has a focused, punchy voice that cuts well as a lead guitar but on the whole is a more intimate instrument.
The OM has different dynamics leading to a different kind of voice. With its lightly braced top matched with the string tension of a long-scale neck, the OM has a more open voice with greater fundamental note separation, a wavering resonance and greater projection, sounding clearer farther away than a 000, which can sound just as loud as an OM to the guitarist, but drops off over distance. Overall, it has a lot more going on behind and around the top voice (fundamental string notes and high harmonics) while the 000 puts most of the energy and sound into that fundamental top voice while the undertone is very much in a supporting role.
But compared to other sizes and types, they remain closely related in look, feel and tone. They are famous for having a more-perfect balance to the volume of each string, compared to all other 14-fret guitars.
This quality is also the hallmark of the 12-fret 00 and the 12-fret D sizes, even though the dynamics and volume vary greatly between the three designs.
Read More at: Martin’s 000 vs. OM, What’s the Diff?
And that is one man’s word on…
Martin Model Designation
Note: This illustration dates from the late 1980s most likely. The MC has the deeper cutaway that was used on the original design, which had an oval soundhole. The Jumbo size is not listed but it has the same silhouette as the M. Sizes SJ and GP were introduced in the twenty-first century.