Most of the emptiers wer accidental... we had some on the Games I did when I was at Impulse. I remember one on a game I did called Spin N Tonic (it didn’t sell too well) where the Reel Roulette code I wrote had a bug which meant it would roll off any symbol it couldn’t allow EXCEPT the Jackpot symbol. That’s what happens when you OR a mask incorrectly (coders will know).
We didn’t find it in test but some player found it in the first week of test in an arcade in Walsall!
Emptied it. Multiple times. So we quickly found out.
If you were clever you never emptied a machine with a cheat/emptier. That would alert us (the manufacturers). If you were clever you’d just take out 50 quid or so from multiple machines.
I still have fond memories of my first emptier on Super Line up back in 83 haha