Gibson MB-1 #920-4
The mandolin-banjo reached its peak of popularity in the 1920s, but as late as 1942 the Gibson catalog was proclaiming this odd hybrid "a necessity in every banjo band for lead or obbligato--ideal for solo playing". The tenor, plectrum, and five-string configurations of the sub-Mastertone style 1 had transitioned to a cast-metal one-piece flange in 1929, but mandolin-necked examples retained the "bracket shoe" construction featuring a flange plate with hexagonal holes as seen on earlier sub-Mastertones.
MB-1 #920-4 (see Gibson banjo serial numbers vs. factory order numbers) was originally shipped on July 23, 1937 to H. Polliack and Co., Ltd., Gibson's leading dealer in South Africa; it bears a "Made in U.S.A." label inside the resonator and a "Made in the U.S.A." stamp on the back of the peghead, as was standard practice for Gibson banjos shipped outside the United States.
Photos courtesy of an anonymous owner.