These locks are usually just cheap "wafer tumbler" locks, probably easier to "pick" than to drill. Start with some other keys as Darcy suggested. You might get lucky. Hopefully your backbox key is hanging on the coin mechanism and you won't have to Macgyver it. I've never had to drill out a lock. Maybe check out the backbox on a similar machine to make sure that drilling the lock won't damage the "backglass holder thingy"