The 15R is a matching rectifier for the 15E UHF pulse Radar triode. Eimac designed the valves in 1940 for the first American airborne Radar. This exhibit is marked for the US Navy.
The peak current required by the triodes could reach 20 Amps and the figure of 30 mA is the average value. The peak pulse power was 5 kW at a repetition rate of 400 Hz and a duration of 2 μS The Va figure above is the PIV rating.
The manufacture of the rectifier is the same as the triode but without the grid cage.
The Navy anchor overprinted in blue.
The enclosed anode gives little detail of the inner construction.
The Eimac box, it is 77 mm square and 90 mm tall. The valve was wrapped in a thick layer of soft wadding.
The wide glass tube envelope is 35 mm in diameter and, excluding the base pins, is 62 mm tall.
Reference: Private communication. Type 15R was first introduced in 1940.