While my coinbox for my custom Arcade was in repair, I built this utility to emulate the sound of coins being inserted anytime the coin buttons were hit on my arcade (I have coin buttons + coin box installed).
After installation asign the keyboard buttons that are assigned to your coin buttons and the utility will play the sounds when they are pressed. In my case I had XPadder map joystick buttons to keyboard characters so this worked for my setup. The utility has a total of 8 different sounds of coins being inserted that are played at random.