EPROM programmer to plug into the PIO port.
Warning: This may not be the correct picture! It may actually be a Henelec or similar unit… It *is* an EPROM programmer though! 🙂 I seem to remember that it would only handle 2708s though. I have used it, but that was many years ago and I can’t remember much about it now.
If this is what I think it is, it was later sold under the Gemini name as G808.