Hi,
Major was acquired by AMSEC a while back so contacting them via this form:
http://www.amsecusa.com/support/ is the best way to start. They may be able to help but will probably not give away any code keys or anything like that via email, but they may direct you to an AMSEC/Major affiliated locksmith or safe technician in your area who could come out, verify you are the rightful owner, and based on the serial number, call the factory and get the code key to make you a new key.
If the keyed door is already open but you just dont have a key to lock it/unlock it, then the easiest thing would be to remove the lock and bring it to a local locksmith or safe shop and have them make a key on the spot. But if that interior compartment is locked, then all you can do is what I wrote in paragraph 1.
If I just read your post correctly, your inside door has 2 key holes and you have 1 key but not the other? (as in an employee key and a manager key needed to open the door?) show us a picture of it to help clear up any confusion, thanks. (upload pics to
http://imgur.com or
http://tinypic.com and then Paste the links here)
Hope this helps, others may chime in later today with better answers or other options,
Squelchtone