Hi, Dick and welcome.
My name is ***** ***** I am also an expert in Safes, here at Just Answer.
I am willing to try to help you get your safe open, if you didn't yet request a refund.
First, the number you state (AY-329552) is the serial number, not the model number. The model number is ***** on a badge-shaped sticker near the upper door hinge, so see if you can find it. Secondly, are you sure your combination is "1, 2, 3?" because that seems a little odd. I would go ahead and request your combination, by submitting a combination request from Sentry, as the previous expert suggested.
Also, if your key is round and hollow, use it first, turn to release the cylinder inside, and REMOVE the key before dialing your combination.
Please let me know if any of these suggestions are helpful. If they are, fantastic! If not, please do not rate negatively, just don't rate at all and either contact Sentry for your correct combination and also to troubleshoot the problem.
I wish you much good luck with your safe and please keep me posted on how things are going. Thanks!