Details
4 pin ballast. Regulates 0.3V to 1.2V at 500mA. Equivalent to Amperite 5E1 and also types 5-1, and 6AA.
Known uses include:
Airline 77, 95, and 108
Arvin 51B
Knight 37B71
Philco 38A
Remler 91
Sentinel 60B, 500, 660BX, and 6200
Stewart Warner 190 (battery)