Ah. Thanks. How did they work, and what are they called (I’ll check out eBay)?
Here's a link.
saminfl:
I don’t think those are rear projection displays. I think the numeric displays are what we called “nixie” tubes.
I can see why you might think that; the slight misalignment of the digits does look like the depth effect seen with Nixie tubes. I hadn't noticed that at first.
I still think they're rear-projection units, based on the quality of the images and their color. The misalignment could be due to misalignment within the projection unit itself. Still, you could be right.
After looking again at the picture, I think those NUMERIC displays are the same as the ones that used to be on gasoline pumps.
They are rotating geared dials with numbers around the periphery. Very much like the dials on radio gear in older private airplanes.
A single feed (specific impulse or voltage) goes to the first digit, and all the other digits are driven by gearing off the first digit.