This 5642 was made in Holland and is an instrument EHT rectifier. The 5642 is a special quality product introduced in 1953.
The spiral coated filament passes centrally within the bright Nickel tube anode. The maximum PIV is 10,000 Volts and the rectified current is 250 μA.
The second picture shows the relation between the filament and the anode.
The thin glass tube envelope is 9 mm in diameter, and excluding the flying leads is 50 mm tall.
Reference: Datasheet. Type 5642 was first introduced in 1953.
Absolute Maximum Operating Conditions¶
Updated February 21, 2013. shape:thin.glass.tube construction:all.glass type:rectifier.hw age:1950.1960 base: pin: