This is a power pentode vacuum tube with a loctal base. This is a spare tube for Register Driver S/N 6. There is a green hand-written inscription '29+FKV4-2' or similar written vertically on the glass envelope.
Date
1945 ca.
Identifying Numbers
Model number
6145
Printed in silver ink on top of the glass envelope.
Other number
DE12861
Stamped in green ink near the bottom of the glass envelope.