Well, it turns out that I had changed mine from the default combination, so that did not help me very much. And of course, I cannot remember what I changed it to. Good thing it is empty. So I wonder if I took it to a locksmith, if they could open it inexpensively and non-destructively? I had just assumed that I was pretty much up the creek. As for taking it back, that gunshop went out of business many years ago. I am not even sure it is a Cannon, since it has no brand name on it.
PS: I am reminded of one time several years ago, when I changed the combination on a small office safe, carefully following the owners' manual, and could not get it to close and latch. I lugged all 90 pounds of it into the locksmith, and in about 45 seconds, they fixed the problem. They also showed me that since the door was open and would not close, all I had to do was lift the door off the hinges and just bring them the door with the dial mechanism, instead of lugging in the whole safe. I am sure they just busted a gut laughing as soon as I left.....