What valve is this.?

thermionic

https://i.imgur.com/Qn5ndPB.jpg

It’s a pavilion built for Belgian company MBLE at the 1958 Universal Exhibition in Brussels. MBLE were an electronics company who produced, among other things, thermionic valves, under the brand name Adzam (which later became Mazda) They later became part of Phillips and then my one-time employer Vishay (who also bought Sprague of Orange Drop fame). Cool story!

Kalimna

I think that is what powers Spinal Tap's "It's one louder, innit?" amps

Penn

That’s an amazing building.