Hi,
Your Bally Big Time was built in 1955, it is a disguised gambling device, the Bally Bingo's were probably the greatest gambling devices ever made, I operated these machines in the U.K. from 1958 till the mid 1960's. Find attached a copy of the original flyer from my collection, there is two books on the subject, Bally Bingo Pinball Machines and The Bingo Wars, United vs Bally 1951-1957. both of these was written by Jefferey Lawton and published by Schiffer. As you know most of the components in the machine are in the back flash, the playfield as only two motors, I strongly suggest you don't try to work on these machines, very few people can fix them, all of the steppers and spotting discs are controlled by one motor, they operate with relays and there are leather clutches on each spotting disc, these need to be stripped out and replaced and soaked in Neats foot oil prior to installing, after saying all of this, they are not very collectible, they still operate these machines in Belgium, where they were deemed to be a National Pastime. I operated these and the cash boxes would overflow with coins, and the cash box is one foot square and 6 inch deep.
Great machines and great memories, if you go to Bally Bingo's in Great Britain, you can read several articles that I wrote for that web site.
Freddy Bailey