Ethan Dicks wrote:
I have something like that with me here in my bag-o-parts... approx 20mm
by 30mm, with a 2mm-thick body made of a rough, dark ceramic, with a 1mm
thick glass top. It's a 2.5 digit display with + and -. All the leads
come through the back of the package in what appears to be a straight-
through fashion (making it easy to figure out how to hook it up).
There is a vendor and part number etched on the face: Sperry SP-738.
I've never tried to hook it up to anything, and have no idea what
voltages it might want. It's a shame it's only 2.5 digits; if it
were 3.5 digits, it might make an interesting 12-hour clock face.
Not sure what I'd need to do that swings from -199 to +199 off the
top of my head.
Temperature?
Your description sounds like the Sperry/Beckman gas-discharge displays, e.g.:
http://www.tube-tester.com/sites/nixie/trade08-panaplex.htm
I think your part number is in there.
Can be cascaded with more digits, or a lot of early DVMs were only 2.5 digits.