I don't know if that can solve your problem, but some of the NeoGeo games, you can configure the 2 coin slots....
1 coin for how many credits... etc.
(actually... some of them are defaulted so that player 1 slot has 1 credit and player 2 has 2 credits...)
however, I don't think older games have it...
on the other hand... if you don't want dedeciated coin buttons, you can also assign the player start button also function as coin button... then you can just press the start button itself to insert coin !!...
hope it helps....
