There are many ways to open these machines without the keys and it is simple in some cases. If you are still interested or need help simply post pictures of the front, and back of the machine so I can advise better as to how and where to get in. Most of the time the keys are locked IN the machine.
(If you do not have a key and your not going to be able to order a new one, it is probably a tubular lock. Unfortunately these locks can not be picked with standard lock picking tools. You need a special "tubular lock pick" and they are pricey. Being they are that expensive you may spend the same amount of money to call a locksmith to your house and have the lock replaced. It will come with new matching keys of course.)
Answers & Comments
There are many ways to open these machines without the keys and it is simple in some cases. If you are still interested or need help simply post pictures of the front, and back of the machine so I can advise better as to how and where to get in. Most of the time the keys are locked IN the machine.
I think you need a barrel key for this. http://www.angelfire.com/ct3/pachislo/PachisloOperation.pdf
http://forums.arcade-museum.com/showthread.php?t=73491
(If you do not have a key and your not going to be able to order a new one, it is probably a tubular lock. Unfortunately these locks can not be picked with standard lock picking tools. You need a special "tubular lock pick" and they are pricey. Being they are that expensive you may spend the same amount of money to call a locksmith to your house and have the lock replaced. It will come with new matching keys of course.)