There are six tubes catalogued in this record. This is a power pentode in a glass envelope with an eight-pin loctal base. This is a spare tube for Bus Driver Arithmetic Rack S/N 10. One of the tubes has a red circle drawn around the perimeter at the top of the tube and "WAD33" handwritten around the envelope near the base in red nail polish.
Date
1959 ca.
Manufacturer
Sylvania
Place Manufactured
U. S.
Identifying Numbers
Model number
7AD7
Printed in silver ink on top of the glass envelope.