Old Cary safe - door stuck?

I have a large old Cary safe (probably about 4X3 may 5x3 includng the cast iron wheels it sits on). It has always worked fine, but I have had no need to go into it in the last year. When I did try to go into it about a month ago, the door would not open. The handle turns and the bolts move, but the door seems stuck - almost as if one of the bolts maybe isn't retracting all the way. I have pulled on the door all I dare and I have had two locksmith's come out but they seem befuddled because everything seems to be working correctly - except that the door is still stuck??? One of the locksmiths say he will probably have to drill it, but becuase he doesn't know excetly where the bolts are located it would be a guessing game and he may have to drill several holes (at considerable expense)! I have a hunch that these guys don't see many of these old safes and maybe just don't know what they're doing . . . can anyone help? At very least I'd think that there is a drawing or schematic of some sort that tels you where the bolts are located if indeed it was necessary to drill it? Thanks.