There are 8 tubes covered by this record. This is a pentode vacuum tube with a loctal base. Pin 5 is missing by design. This is a spare tube for Bus Driver-Arithmetic Rack S/N 10. None of the tubes have additional legible markings on their envelopes.
Date
1938 ca.
Manufacturer
Sylvania
Place Manufactured
U. S.
Identifying Numbers
Model number
7AK7
Printed in brown ink on top of the glass envelope.