The WD12 was designed by Westinghouse Canada and released in 1923 as the successor to the WD11 electrically they have the same characteristics. The difference is in the base, the WD11 has a four pin base and the WD12 has the UV base.
The WD12 is a high vacuum valve designed for use as an amplifier or a detector. and was one of the first hard valves available to the American experimenter.
Originally the WD12 was made with a brass shell base cap. This is of later manufacture and has a Bakelite base cap.
The UV base and pins. These are plain cylinders as they twisted into/onto the bayonet base springs.
The Westinghouse name on the dome.
The internal structure is partly hidden by the gettering.
The wide glass tube envelope is 25 mm in diameter and, excluding the UV base pins, is 83 mm tall.
References: Data-sheet (Tube Collectors Association), 3001 & 1047. Type WD12 was first introduced in 1923. See also1923 adverts.
