Expert: Rodger Knutson - 10/26/2011

Question
In the late 50s, early 60s, some JDs developed the scheme of drilling a coin and attaching a thread to it. This allowed the theft to recall the coin after dropping it in the coin slot and rack up extra credit for the same coin.

How did vending machine operators defeat this theft?

Answer
Hi Curtis,

Hey......, Now that is a refreshing question and the first time anyone asked about this. We all heard about the string and drilling a small whole in the coin or gluing the string to the coin. The coin would move on down the coin acceptor/rejector and trip the coin switch wire that would tell the machine that the coin was accepted. It was then at that time the string was pulled, and the coin came back out the same way it went in. With mechanical acceptors or rejectors used in those days, to solve this problem the operators would install a newly invented add on device to the coin acceptor, which was really a razor blade like plate that was bent out some on the bottom, when the coin slid over that plate on it's travel through the acceptor, and was pulled back by the string, the string cutter plate would simply cut the string. The operator would then get his coin and some of the cheaters string to boot. The later electronic coin acceptors solve this problem via using several emitters/receivers in the coin mechanisms channel and the coin must pass between these emitters and receivers. These emitters/receivers would detect any reverse travel of the coin, or slow travel, and report this information to the MPU or the games computer. The computer would then respond using it's pre programmed instructions stored on proms. In this case the computer would respond by putting the machine in a tilt mode, and flashing a error code on it's display. This error code would then tell the technician that there was a reverse coin error, or other related coin handling errors. Then the technician would open the machine and inspect these areas for problems and reset the machine when he was done. There you have it Curtis, and I was so pumped up by your question I went back to some very old part suppler catalogs, and found this "string Cutter" option part in one of the old catalogs I have still and scanned it for you, so you could see what this little hummer looks like up close and in person. That photo is attached to this answer, so click on the photo to see a good enlargement of this part, the "string cutter" used in the old mechanical coin rejector/acceptors.

Thank You for asking about this!

Rodger Knutson
http://www.coinslots.com