the standard bally games shipped with the round tubular cam/"ace" lock in the door since they are higher security. Other external locks were often flat style, so there was a mix of lock types on the game.
it was common for a customer to replace locks with their own that were keyed the same. When those machines were removed from service, the locks would be removed unless the common key was no longer being used. The purchaser would stick in whatever they had.
you can get either flat or tubular locks easily ... pinball parts suppliers, amazon, ebay, etc. It's a lot cheaper to drill out and replace a lock than get a locksmith to pick and make a key for what you have.