Printed in silver ink on the top of the glass envelope.
overall: 3 in x 1 1/4 in x 1 1/4 in
This is a pentode tube enclosed in a glass envelope with a loctal base. Pin 5 is missing by design. This tube type was specially designed for long life, originally for use in the Whirlwind project. This is a spare tube for Register Driver S/N 6.