Printed in silver ink on top of the glass envelope.
Stamped in green ink near the bottom of the glass envelope.
overall: 2 7/8 in x 1 1/8 in x 1 1/8 in
This is a power pentode vacuum tube with a loctal base. This is a spare tube for Register Driver S/N 6. There is a green hand-written inscription '29+FKV4-2' or similar written vertically on the glass envelope.