Instead of posting this in the classified section, do a forum search about missing keys. You will get better results. Its likely that you will need to drill out the lock - I doubt you can see the lock number, so unless there's a wild stroke of luck, any key you try will not work.

Concerning the coin door: You will need to buy a lock from a parts supplier - again, do a forum search - everyone has their favorite vendor. You will have to decide who you want buy from.

Have you looked for a hook on the inside of the coin door or on the inside of the cabinet for the backbox key? Often times, the key is hung there. Look well before drilling out the lock.

no key for pin
Gottlieb System 1 - Backbox won't open
Key broken off in backbox lock (Solved!)
Lost key for Firepower backbox..

These are the subject lines for the search I did. There's a video in one of these that may help. I didn't watch it, so I can't offer an opinion.