There was something similar done with a machine called Jolly Card. Hacked ROMs were widespread, but they got replaced soon and chips sealed to that replacement could be spotted. But then people reverse-engineered the ROM and found a flaw in the random number generator. Smart Bulgarians managed to fit a single chip computer into a car remote, which at the time was a significant accomplishment. So, after using the remote keys to allow the device to sync with the poker machine's timer, they were able to guess the part when you can double your wins. So, after syncing, the smallest win can be increased 1,024-fold (you got a maximum of 10 doublings). They were selling this remote for 10,000 DEM, or German Marks, which was about 7,200 USD at the time. After people made millions milking the poker machines in Western Europe, the manufacturer released a fix, and the new generation of machines got a hardware random number generator.

I remember some mafia guys came to me knowing I can replicate the hacked ROMs, so, I cloned it, but I also made a hard-to-notice mark so that I can identify these machine (well, it was an extra space in some text.) Well, unfortunately, I wasn't able to find one later, but I didn't look hard for one anyway.