I did a project on this about 30 years ago. The safe cracker told me the key was to know the brand of safe you were working on as all of them had their tricks.

But once the tricks were known they were easy to defeat.

So look it over and see if you can find a brand name and model number. Then do a search for opening that safe.

I think what you have is more likely a 'fireproof box' in that it would survive a 90 minute fire. Not that knowing this makes it any easier to get into.

And for even more fun you might open the main door only to find several smaller 'safes' built into the interior.

Keep us informed. There is no telling what you might uncover.