The 1st reel snap switch

[OldReno]

The first reel snap switch.

This is one of those Bally add-ons that came out as a 'protection' device.  I certainly don't know for certain why they added it, but I can tell you what it does (as far as my limited knowledge goes). 
If you play 4 coins, and time it just exactly right, when you insert the 5th coin, and just at the right time pull the handle, the machine will reset to show one coin played.  With a little practice you can do this over 50% of the time.
The snap switch, by some mumbo jumbo circuitry prevents that from happening. 
I don't think this was a measure to prevent cheating, rather, a means to keep people from losing their odds, especially when they hit a jackpot, and saw that they only had registered one coin in. (Nothing more fun than a floor Beef with a drunken customer about why they didn't get that jackpot....sarcasm)
So I'm thinking it's less an anti cheat device, and more of a customer protection (and casino hassle) mechanism.
Hopefully OpBell or some other Bally Guru here can weigh in on this more, and possibly explain the circuitry to us.  I do not have a schematic with this circuit in it, and it's very probable I could not understand just how it works anyway.
So, that's my latest post to you-all to help forward more information on the infamous and incredible Bally ElectroMechanical slot machine that we all adore.