Three tubes are included in this record. This is a Sylvania developmental 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.
Date
1925 ca.
Manufacturer
Sylvania
Place Manufactured
U. S.
Identifying Numbers
Model number
SR1407
Printed in silver ink on top of the glass envelope.
Other number
9RD1 V1-2
Handwritten vertically in green ink on the glass envelope of the same tube.
Other number
AD7007
Stamped in green ink near the bottom of the glass envelope on one of the tubes.
