Hello, and thanks for requesting me to help with your question.
Because combinations are not available online, the only way to retrieve your lost combination and keys is contact the manufacturer. Sisco is now owned by Hollywood Safes, and you can follow directions and fill out the form at this site, to send to them:
CLICK HERE You will need to verify safe ownership, also, most likely with a notarized form. You will see their contact phone numbers on the form, but for your convenience, I've included it here: 1-***-***-**** Their hours are 7AM - 5PM Pacific time, but are subject to change.
The only other alternative is to call a local safe technician/locksmith to try to open the safe without damaging it (or drilling it open).
I hope this helped and wish you much good luck with your safe!
Please be so kind as to rate my answer with positive feedback, as that is the only way I receive recognition for my assistance. Thank you very much!
Providing a positive rating will not end our conversation, should you need me for any follow-up. Simply click 'Reply' for clarification or additional information, if needed.