1954 RB-250 with FON 4-2462-35. This is a sold instrument from the Picker’s Supply website. Here is the description:
The Gibson Mastertone model RB-250 is pretty much the banjo to have for bluegrass players. Mahogany resonator, maple rim, bound rosewood fingerboard with ‘Mastertone’ inlaid on the penultimate fret. This was the first year for the 250 models and this has an arch top tone ring, one piece flange , bound center-dip ‘dove wing’ peghead with crown inlay. Optional at the time, this banjo also has quick tune tuning mechanisms installed probably by Gibson.