[SiriusHardware]

Yes, I got a similarly chatty reply from him, he was very helpful and added the extra detail at my request. I have a couple of the red DP-less ones on the way to me.

If only green would do, then I imagine it would not be impossible to fit a more modern display and reroute the segment signals from the channel switch to the right pins on the new display, because you seemed to say that the original green display you bought does physically fit. Of course an exact drop-in replacement is always to be preferred, if available.

Your picture of the very similar original green one gives me some hope that these red ones will at least be pin-compatible.

I would leave the green one stolen from the Harvard in the Rotel, where the green channel display is very much part of their signature 'look', and put a red one in the Harvard.

Edit: If you'll recall, the service manual entry for the same part in the similar Cybernet 3000 described it as 'Common-A' - common anode. If you have a DMM with a 'diode test' feature they can often light LEDs dimly just by themselves, so that can be another quick way to find out whether a display is common anode or common cathode.