I think I'm okay with this one, but I'm going to ask just to be safe. My boards match perfectly with the MVS-Scans.com set #3, except for on board 2 where I have a windowed eprom. See picture.
You're fine, that may just be repair. The "27C1001" beside the chip is actually the part number of an eprom chip, which puzzles me as to why the one on MVS scans is a mask rom. But hey, as long as it works.
Your cart is legit. Some of the early titles had eproms for some of the roms. Occasionally you'll see an OTP eprom in place of a ceramic windowed eprom. Those generally get mistaken for mask roms.