Martin OM-18 History And Changes: 1930 To 1934

OM-18 Changes By Year

1930: The Mahogany Orchestra Model

The first OM-18 shop order was placed in January 1930. The design combined a spruce top and mahogany back and sides with a 14-fret neck joint and approximately 25.4-inch scale. Its ebony fingerboard and bridge, simple dot markers and restrained trim distinguished Style 18 from the rosewood OM-28.

The Orchestra Model body was derived from the 000, with a shorter upper body to expose fourteen frets. The original OM-18 neck used bar frets and an ebony reinforcement strip. The later steel T-bar neck system had not yet entered production.

1930: The Belly Bridge Replaces The Straight Bridge

The earliest OM-18 design used a plain straight bridge. During 1930, Martin adopted the belly bridge, widening the bridge behind the pin row. This was a change in the bridge’s footprint, not a change from mahogany to rosewood back and sides.

The bridge transition also affected the OM-28, whose earliest bridge had pyramid ends. Some earlier instruments still in factory stock received the new belly bridge before sale, so the original production sequence can include factory-updated guitars.

1931: Larger Pickguards And Guitar Tuners

The small teardrop pickguard gave way to a larger guard during 1931. Banjo-style tuners, with their mechanisms projecting behind the headstock, were also replaced by conventional open-back guitar tuners that year.

These were separate transitions. A larger guard did not necessarily arrive at exactly the same time as the newer tuner set. Later original OM-18s commonly combine the full-size guard with open-back Grover machines.

1932 And 1933: The Longer Dot Pattern

Early Style 18 fingerboard markers occupied the fifth, seventh and ninth frets. In early 1932, the pattern extended to the twelfth and fifteenth frets. The additional markers are a dated decoration change within the original OM-18 run.

The OM-18 continued through 1933 with the long scale, 14-fret body and bar-fret neck construction. Its mahogany body remained the defining material difference from the OM-28.

1934: The Name Changes Before The Scale

Martin changed the designation to 000-18 in 1934. The earliest guitars under the new name still had the long scale. Later that year, the scale shortened to approximately 24.9 inches.

T-shaped frets and steel T-bar neck reinforcement also entered production in 1934. Those changes belong to the successor 000 era. The Martin small-body guide follows the later 000 family.

Did All Original OM-18s Have Banjo Tuners?

No. Banjo-style tuners belong to the earlier production, followed by conventional open-back guitar machines during 1931. Both types occur in the original OM-18 period.

Is An Early Long-Scale 000-18 An OM-18?

It shares much of the preceding OM design, but Martin designated it 000-18. The 1934 name change and later scale change were separate events, so long scale alone does not supply the factory model name.