[ironmill]

Hi Jim and welcome,
It was a common practice in post war sets to use  whatever tubes where available do to war shortages. Have serviced sets with a combo of miniature, locktal, and octal all on one chassis. Electrically the tube are the same just different pin outs. 50A5, 50B5, 50C5, 50L6 all the same barring the socket connections. By the early '50s most had gone with using miniatures and the 50C5 replaced the 50B5 because of the pin layout was prone to have plate to heater shorts.

Thanks Terry.

Regards,
Jim