Summary

This is an example of a Cosmos 'Short Path' valve. The electrode structure is long and thin, giving the electrons a shorter (as the name implies) distance to travel than in many valves of the period. It is a general purpose triode. There were four varieties of the SP18: Green, Blue, Red and Red Red, all with different characteristics and identified by a coloured spot on the bulb (two in the case of the RR). 1.8 volt directly heated cathode.
Manufacturer: Metropolitan Vickers Electrical Co. Ltd., England.

Physical Description

Tall cylindrical bulb on small 4 pin UX style base, mounted on display block. Exhaust tip on top appears to be broken. Red spot on bulb indicates the selection group of the valve,

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