Mullard master valve in its original box.
Mullard PM22A 5-pin master valve in its original box (130 x 50 x 50 mm) used to power a radio from a 120V battery, probably in use from the mid-1920s until the 1950s.
Mullard master valve in its original box.
Mullard PM22A 5-pin master valve in its original box (130 x 50 x 50 mm) used to power a radio from a 120V battery, probably in use from the mid-1920s until the 1950s.