Pictures:

Details:
The Amperex 258-B is a half-wave Mercury-Vapor rectifier tube used in power supplies. Identical to CV2594.
Filament Vf 2.5 Volts / If: 7.5 Ampere / -: Direct /
Description 7.5KV PIV, 640mA. Bi-pin version of 249B.
Amperex, Continental, Hytron, Taylor and WE known manufacturers.
Literature Taschenbuch zum Röhren-Codex 1948/49
– – Manufacturers Literature
Tube Lore, Sibley, USA 1996

Datasheet:
n/a

Links:
258-B on Radiomuseum