For the raid in the early '60's, the Fed's "cased the joint" before they did the raid. They sent in agents in advance who made the rounds observing where the machines were, what kind and how many. They spent time in the bars logging the approximate play and cash generated. They used that information in the tax cases they brought against the owners.
If any of the owners moved machines before or during the raid, it didn't do much good because they had been watched for some time prior to the action. I heard a few stories from my Father who was involved with several Fraternal organizations that got whacked pretty hard. I don't remember if anybody went to jail, but I'm sure there was a lot of money ponied up for back taxes that probably offset some hard time.
I heard that when they did the raid in Butte, they ordered all the bars to close up and lock up. The busiest guys in town after that were the locksmiths, installing locks on bar doors that had never closed long enough to need them.