Gibson TB-3 Mastertone #9551-17

Style 3, the least expensive model in Gibson’s prewar Mastertone line, was revamped in 1929.  The model’s straight-grained maple changed to mahogany, two concentric rings of white/black/white purfling were added to the back of the resonator, the brass tube-and-plate flange was replaced by a one-piece cast metal flange, and the headstock shape and inlay patterns also changed.  #9551-17 (see Gibson banjo serial numbers vs. factory order numbers) dates to the following year; originally a tenor banjo with a raised-head tone ring, it has now been converted to five-string flathead with a neck and tone ring by Steve Huber:

Photos courtesy of an anonymous collector.