These rare 7 segment displays once used in HP calculators are still quite impressive if you are lucky enough to find some.
Yes they are inefficient. But nothing compares to the deep red glow of those sharp and tiny GaAsP LED segments.
This interface board features 8 current limiting resistors for the segments and two tiny latched qfn shift registers. One for the anodes and one for the cathodes. This makes it simple to interface with modern microcontrollers (Example arduino sketch provided in files).
The left one is a 7415 and the right one the 7405 with the centered dot.
Probably nothing more to say here. Its a 7 segment interface board. But for some very special displays :)
If you still have some around grab the design files from the files section and make them useful again.
Used like a normal shift register based 7 segment module.
First write the digit (low active, 0b11111110 for first digit), then the segments (a-dp, a = lsb, high active).
See example for more info.