This is the third banjo in the famous batch of rare RB-75's, one of which is Curtis McPeake's "Old Betsy" and one belongs to Charlie Cushman (see F 906-1 and -2). This third one from the batch has lost its original fingerboard, and has been refinished. No serial number is stamped in the rim, and there is no decal.
Note the old-style "diamonds & squares" peghead inlay scheme. Undoubtedly these were leftovers in the late thirties when this batch was produced.