It is easier to drill from the back to access the tumblers using a manipulation tool so the doors could be opened. Locksmiths also have a list of most common combinations if someone has the patience to sit there and try them.
One warning, I do not think this one is old enough to qualify, but some safes actually had a poison gas capsule mounted directly behind the spinner to thwart attempted drilling. I know it sounds crazy, I learned this from a High Haz Specialist from the UK who encountered one.