So, what valves have you got, or come across that are not like anything else you've ever seen?
1538-P1 strobotron.
A very small dome shaped 9-pin valve
Pics & info here: http://www.tubecollector.org/1538-p1.htm
A couple of years ago I sold 3 of these for a very pleasantly high price to a great gent in the States who had been trying for years to find some spares for his old machine.
They're a very high speed flash device (high speed in the sense that the flash period is very short) used in a 'Strobotac' which is a piece of gear for measuring very high speed motion - (no bowel or toilet jokes please)
http://www.tpub.com/neets/book16/67c.htm