I'm in possession of a Psygnosis / SN Systems PSY-Q CD Emulator System board, which apparently was used in PS1 (and maybe Saturn?) game development as part of their PSY-Q dev kit setup. No idea if it works or what its value might be to a collector; hesitant to just bung it on eBay as it seems to be very obscure and specialist.

Documentation's out there for the PSY-Q system itself, but the CD emulator board only crops up in this one archived listing, where it apparently sold for $138... no idea when though:

Opinions, anyone? Happy to entertain offers too, if you're so inclined.

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(Note the rather ancient sticker on one of the ROM chips declaring it "working" as of 1997 )