Hmmm, I dont have an idea for any type of tack button, but I was thinking of putting some sort of toggle switch. The toggle would have to require a light touch, like a "paper thin" toggle, so that when a coin hits the toggle the switch would record a "1". I was thinking of placing 4 of these switches above the coin holes so that when coins are sliding down the ramp I could tell if how many switches were activated.