For sale (1 case of 10 Incandescent bulbs) Clear, 100 hour, 50CP, C-6 Filament, 57.1mm MOL.  

Volts:  5.5

Watts:   34.38

Amps: 6.25

Shape:  RP11 
Base type:  SC Bayonet, BA15s, Single Contact Bayonet  

Used in Older Model J & L Comparators  BC14, FC30, PC14.