assuming the manual is right - which for the earlier bingos it probably is - if the rivet in the diagram has no wire id in it, it's not used.

someone added the white wire and I assume the other one if it's the same. In general, wiring unused rivets someplace will make the game more liberal.

what ya do is look at the other rivets in the same ring and see what they control. In this case, the outer ring of rivets is wiper D, which the spotting disc diagram says is wire 45-10 at schem F-28.

wiper D is feeding four wires all going to the magic squares feature unit (MSFU), and all are used in the MSFU step-up coil circuit. You'd attach the loose end of each wire to one of wire 41-7, 57-4, 60 or 36-8 on the spotting disc. If you want to improve the chances of enabling all the squares, connect to 41-7.

if you just want to improve the odds of getting the ABC squares enabled, connect to 36-8.

the MSFU is a 9 step unit. If you plod thru the schematic and manual diagram (look at when the lamps turn on), you'll find:

- step 5 : ABC enables
- step 9 : D enables

while either 41-7 or 57-4 can step the unit to the 9th step, 41-7 can "run" the unit from any step to the enabling D on the same cycle (coin/credit played). 57-4 cannot run to D, tho it will run to the 7th step and going from step 7 to step 8 is guaranteed on the next cycle, then 57-4 can enable D on the cycle after that.

spoiler alert:

if you look at the MSFU and schematic closely, you'll find the arrow lights implying you are "getting closer to enabling ABC" are completely meaningless. Your MSFU controlled odds of getting to step 5 in one cycle are the same when the MSFU is on any step 0-4.

note wire 60 is only used to run the lights to the right most arrow at step 4, but that doesn't change the fact that at all steps 0-4, wire 25-6 is connected to 36-8, 41-7 and 57-4, so step 4 is the same as reset wrt to enabling ABC.

this kinda thing is common in the design. The extra balls works similarly ... lighting "1st" and "extra" make no difference on most games - you can only get "ball" when the run circuit connects, and that would light all three panels at the same time.

this simplified the statistical odds calculations for the entire game which was done to figure out how many rivets on the mixers and spotting disc to wire into a specific circuit.

it's common - especially on the first machines of any particular game type - to have rivets wired out to lugs on the mixers and spotting discs that aren't jumpered/connected to game harness wiring. This let bally add/remove rivets by adding jumpers on the lugs if they found the game was paying back too little/much to the player. afaik, they never published the specifics, but you could see on the spotting disc diagram (when provided) what to do. The mixers you'd need to get the factory blueprints or reverse-engineer the connections.

the mixer diagrams are available on https://bingo.cdyn.com/machines/bally/key_west/

'course, most operators were concerned with making the game pay back less, so they wanted to know what wires to cut