While I wait for parts to use the 7-segment Soviet displays, I picked up a few HP units that will fit on a breadboard. I already verified the driver chips are functional, so I didn't really need these new displays, but I got them anyway. They seem to work fine and I really like their all-red look. The part number is 5082-7653. I've also worked on a rough draft of the circuit board, once the new parts arrive I'll verify some measurements and get the boards ordered.