The Schickerling S-900 only has information on the base cap. The filament current indicates that it is a bright emitter. The internal silvering shows that it was a hard vacuum type with gettering. The design purpose was as an amplifier.
Thanks to Joe Gruber for sending the image.
The envelope is mm in diameter and, excluding the UV base pins, is mm tall.
Reference: Joe Gruber.
Absolute Maximum Operating Conditions¶
Updated February 12, 2021.