Not to be confused with the credits display.
Coin counters are internal electromechanical devices used to count inserted coins in arcade cabs. They can only count up and should be made hard to reset.
The counters typically have one pin hardwired to +12V, and the other one connected to the MVS board by JAMMA pins 8 and J. They are operated by software, not directly by the coin chutes.
Only the system ROM should take care of this.