Crystal Mines in Athena 5 screw cart with soldered windowed EPROM, the heck?

[Niku-Sama]

so I was going through my trade bait for PRGE and I had a complete copy of Crystal Mines from Color Dreams. its on ok shape, manual was laminated as it was a previous rental. I popped it in to my top loader and it wont work. it boots to a scrambled screen.
well crap.

but I remembered I had another copy I bought years ago as Athena and found it had crystal mines in it instead, so I thought I might as well swap PCBs because the Athena one worked. so I cracked them both open, tried cleaning the complete one to no avail so I opened Athena up. its been missing 2 screws since I bought it and the screw holes were widened a little near the top for some reason. I open it up and I notice theres a windowed EPROM with a red sticker over the window.
the complete copy has a MASK rom. the Athena cart wasn't as nicely put together as the complete one I had.

is this normal or did I find a thing?

also these are probably not going to be trade bait any more

[Tanooki]

Hard to say without pictures, could be something color dreams was working on (proto/tester) to a bootleg.

[Gameguy]

Need to see pictures to be sure, it could either be a repro/bootleg, or it's a legit prototype.

[SparTonberry]

It's POSSIBLE to be a prototype, since Color Dreams was an unlicensed developer they couldn't get official proto carts, so I think they even said they hacked up retail carts to use as dev carts.

[understatement]

It's POSSIBLE to be a prototype, since Color Dreams was an unlicensed developer they couldn't get official proto carts, so I think they even said they hacked up retail carts to use as dev carts.

I want to say I've heard this somewhere as well, but I can't seem to find anything on it now to back it up. It makes sense though But yea pictures would be awesome.