Serial number 39944 is a 1929 00-28. It was stamped on October 16, 1929 and cleared final inspection on March 5, 1930. Being almost 5 months in production was very unusual for the time, especially since it appears the batch the guitar comes from were out of the finish shop on November 12, 1929. Clearly, Martin must have more important priorities at the beginning of the Depression. Either that, or the demand for 00-28 guitars was low at the time and there was no need to rush a batch through production. (As an aside, almost all Martin shop order slips are marked "RUSH").
The tuners are Waverly G-32 machines.
Style 18 features:
Back and sides: Brazilian rosewood
Top: Red spruce(Adirondack)
Back stripe: Zig-zag purfling
Other period features:
Ebony belly bridge
Ebony bar neck reinforcement
1-7/8" neck width at nut
24.9” scale length
Tortoiseshell celluloid pick guard
Slotted diamond and square fingerboard inlays
C. F. Martin stamp on back of headstock
No style stamp