Gibson prewar banjos typically came with one of three neck varieties. Tenor and plectrum necks were both 4-string necks. Tenor necks were shorter and generally had 19 frets. Plectrum necks were longer and had 22 frets. 5-string necks were the same length as plectrum necks but were wider to accommodate the fifth string. The two letter prefix often mentioned with the style of a banjo was determined by the type of neck on that banjo. The abbreviation TB stood for “tenor banjo”, PB for “plectrum banjo”, and RB for “regular banjo” (5-string).
Most prewar Gibson banjo necks have a one-way adjustable truss rod that allows the neck to be straightened to remove any extra bow and make the banjo playable.