[time-nuts] Old Crystal.

[ed breya]

I just took a quick look. I have four of these ovens, definitely marked 
for the HP5110A. One is partly disassembled so the crystal can be 
pulled. It looks very much like the one in the picture that Jeremy put 
up. There are two quite large mica caps mounted on a disc-shaped board 
along with the crystal's (two) soldered leads. That's all that goes 
inside the oven. The envelope definitely looks like an octal tube type, 
and the crystal is double-convex - you can see it edge-on, or tell by 
looking at your reflection from either side. The surfaces appear to be 
gold plated. The bulb of this one appears marked with "35" and "01" 
(or"10").

So, if you look up the HP51110A, you'll find a workable oscillator circuit.

Ed