U8 Osram balloon directly heated rectifier nickel plate V shaped oxide filament Holy Grail

Description

This is a VERY early (circa 1930) Osram U8 balloon shape with a horizntal cut section anode, we call it the Holy Grail of audio valves.

The U8 is a directly heated rectifier.

Unlike the later version the “U8” is etched at side of envelope.

Nickel plate with a single V shaped filament supported by a single tension spring.

In full emission and working order.