There are 6 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. Five of the six tubes described in this have additional markings on their envelopes, as described above.
Date
1938 ca.
Manufacturer
Sylvania
Place Manufactured
U. S.
Identifying Numbers
Model number
7AK7
Printed in brown ink on top of the glass envelope.
Other number
20.FR.V2-1
Handwritten vertically in green ink on the glass envelope of one of the tubes.
Other number
67.FR.V2-1
Handwritten vertically in green ink on the glass envelope of one of the tubes.
Other number
8AR V-4
Handwritten in white ink around the glass envelope near the top of one of the tubes.
Other number
AK1320
Handwritten in white ink around the glass envelope near the base of one of the tubes.
Other number
AK2213
Handwritten in white ink around the glass envelope near the base of one of the tubes.