I had held my hand, expecting some of the American technicians to answer first. As they haven’t I will start the ball rolling.
I can’t tell you what the safe is. Somebody else might be able to.
As it is a Sargent & Greenleaf combination wheel it is extremely probable that the lock is also an S & G. Without wishing to be disparaging to your safe, it is unlikely that it is anything more than any one of their 3 wheel models. Whilst a very good lock, offering a high degree of security, it is by no means invulnerable. Any good locksmith ought to be able to manipulate it open for you. That is probably the best way to go. If you do this you will then have a fully functioning safe and can change the combination to one of your own choice. Whilst there the locksmith would be able to clean and service the lock, and the boltwork etc. of the safe and probably tell you exactly what you have got.
The alternative would be to drill it open or cut it open. Of course if you do that there will be damage to the unit which would need to be repaired. Some insurance companies will never give you coverage on a safe that has been opened in this way.
One thing which I would urge on you is to do something! This can never be reiterated too many times. NEVER HAVE A SAFE IN YOUR HOME WHICH IS LOCKED CLOSED AND TO WHICH YOU CANNOT GET ACCESS! I hope it never happens but if you were to be burgled when you are actually at home, the miscreants are likely to ask you politely to open the safe. If you can’t they will assume that you are being stubborn and might well become progressively less polite in their requests. THIS DOES HAPPEN!