old 7-segment displays

Hi all, (not sure if I have posting access here - guess I'll find out soon enough!) The recent messages about displays have made me recall a bunch of little devices I have stashed in a box someplace... They're mounted on a board in such a way that they look like they're the display panel for an ancient fuel pump, but I could be wrong. There's two sizes, one about an inch high and the other about 3/4", and some of them are double-digit within the same housing. These things are glass, with a black background and silver segments - there's a lot of discolourment on some of them around the segments on the rear of the glass facing. Pins come out of the rear of the devices. Any ideas what these could be? Some sort of mercury vapour or something? It'd be nice to hook them up - I bought them from a car boot sale a few years ago and never got around to doing anything with them. I can probably work out which pins drive what, but have no idea what sort of voltage these things will need (I'll try to remember and get whatever text info there is on the PCB itself - think it was just a bunch of part numbers, but there might be something meaningful to someone if the board didn't just come from something as mundane as a fuel pump) cheers Jules