What do you make of this?

[Mike Watterson]

A 5476 is British Admiralty store reference for NU30 / CV1278 silica rectifier.

Silica envelope vacuum rectifier. Used in radar modulators. Graded glass seals
60 kV anode voltage
0.8 A current
1.8 kW plate dissipation
90 mm bulb diameter

So obviously the 5476 isn't useful as a part number.