I hope you didn't pay too much for the safe.
My recommendation is to bring it to your local locksmith and have him open
it for you. There are no trial combinations, and I do not believe the
factory will send the factory combination out for the asking for obvious
I average about 15 minutes to open a sentry. No holes, no damage. I use a
stethoscope, hair dryer, paper clip pounded flat, and some sand paper for my
OTOH, I might be full of nonsense. Except for the 15 minute part. My fastest
was 8 minutes. with three witnesses, but that was 10 plus years ago, and
they likely won't remember. Slowest was about 45 minutes.
They will give it to a locksmith who is a (verifiable) member of ALOA,
SAVTA, or NSO.
The locksmith will confirm ownership and provide the combination to the
customer (for a fee of course)
Now this is assuming that a) the serial number is available AND b) the
combination has not been changed.
5380 apparently is not a current production model with the newer wheel pack,
therefore manipulation is an alternative option. (Manipulation is not
practical with the new wheel pack units because of it's design)
Contact a local locksmith or safe tech if you want it opened. (If they say
they have to drill or damage it, call someone else.