I bought a nice, barely used, hardshell guitar case for my son's birthday. It's in extremely good condition and the combination lock on the case has never been set, but the card telling how to set it was missing. The store where I bought it don't have a clue. They'll let me return it, but I'd rather keep it. There is no brand name on the case, so I can't ask the maker.

So. How do you set the combination? The lock has four dials (all currently at zero). Anyone have experience with this?