In this case it looks like it was marked bad dump. But really a good dump but something else was wrong. It is why they keep bad dumps in there. Sometimes it is a resistor on the board tagging something in the code. I have one device that I do not think is in MAME yet. It has 4 games inside it. But it is sold as 4 different units and they just change the board config to make it boot different games. But the binary is the same on all 4 units.
It is also good to go re-checking things. As new dumps show up sometimes. The problem people are starting to see though is MAME is see as a 'golden copy' and people are using it to make fixes/changes to real board. Then those boards end back up in the hands of people doing dumping and it becomes unsure if it is a verified dump or something else. Or people see the game in the list and say 'good enough' but it is actually a revision of the game. There is a whole site dedicated to that (not sure how up to date it is) unmamed.
> In this case it looks like it was marked bad dump. But really a good dump but something else was wrong.
No, it sounds like it was a bad dump. This writer found that they were able to get a different bad dump from the same game, but then when they ensured good contact with the reader, they managed to get a good dump that was a duplicate of another rom.
It seems that for this arcade system, the roms for Taiwan and Mainland China are usually the same, with some system board setting? triggering use of Traditional vs Simplified writing, but when the taiwainese packaged game was dumped with errors, it didn't match; when dumped properly, it does match the mainland rom.
It is also good to go re-checking things. As new dumps show up sometimes. The problem people are starting to see though is MAME is see as a 'golden copy' and people are using it to make fixes/changes to real board. Then those boards end back up in the hands of people doing dumping and it becomes unsure if it is a verified dump or something else. Or people see the game in the list and say 'good enough' but it is actually a revision of the game. There is a whole site dedicated to that (not sure how up to date it is) unmamed.