Gibson TB #165
Gibson's first banjo model was known simply as the TB, for tenor banjo, and was introduced in 1919. The tenor banjo had been devised shortly after turn of the century; its CGDA tuning made it easier for mandolin players to make the transition to the increasingly popular banjo, and within a few years the tenor had largely eclipsed the original five-string version or, as Gibson called it, the "regular banjo".
Gibson's first banjo design was open-backed and featured a single wooden dowel for neck attachment. A small-diameter metal hoop atop the wooden rim served as a rudimentary tone ring. The very earliest examples included a silver plate engraved "Gibson / Mandolin-Guitar Co. / Kalamazoo, Mich." attached to the dowel stick.
Photos courtesy of David Marks.