The SN-146 is a triode made for the Japanese military in WWII. The Handbook on Japanese Military Forces (1944) lists the SN-146 being used in the Model 92 (1000 watt) and Model 95 (500 watt) transmitters. The plate is made in two sections as seen in the third photo. This example was made by Tokyo Electric and was once part of the Howard Schrader collection.

Length = 17.50" Diameter = 7.50"
Max voltage = 3500
Max current = 600 ma
Fil voltage = 13
Fil current = 25 amps         GOTO INDEX