The VM4V is a battery variable μ RF screened grid valve for use in broadcast receivers.
The top cap follows the early 1930s pattern of a screw down connector. In this exhibit the insulated cap is missing.
The balloon envelope is 49 mm in diameter, and excluding the B5 base pins is 120 mm tall.
Reference: 1043. Type VM4V was first introduced in 1932.
Absolute Maximum Operating Conditions¶
Updated April 11, 2013.