Serial number 38521 was stamped on May 1, 1929 and cleared final inspection on June 13 that year.
As a 1929 guitar it would have originally been made with a pyramid bridge. However, 1929 was also the year that the OM guitars were introduced and once that genie was out of the bottle the demand for 12-fret 000 guitars decreased significantly. The belly bridge appears to be the early version with a shallow saddle angle, something that would be appropriate for an early 1930's Martin guitar.
Martin had nineteen 000-28 guitars in stock at the January 1, 1930 inventory count. Martin switched from using pyramid bridges to the belly bridges at the end of the first week of April 1930. If this guitar was sold after this date then it would have been updated at the factory by replacing the pyramid bridge with a belly bridge, so the bridge may be original to the guitar.