Thanks for the 'electricals' pics!
Definitely a triple XXX Home brew.
DCC90; would appear to be an RF double triode. Used as an RF amplifier and/or oscillator
. Possibly in the UHF band.
Trying to find some decent specs on it.
If yours is dud there are still some around for a tenner or so;
Must dig around in the cellar; somewhere I have a box of valves too!
(Surprise surprise! I hear you say😉)
Cheers, Doug 😎
PS Here some history and data on the bottle. Up to 40Mhz apparently.
PPS Valve data now attached in the PDF😊