To the original poster: Thanks for asking our advice. I am surprised that this thread has gone on so long for a relatively simple question. But the fact is that anyone who invents a cartridge gets to name it whatever they want whether it makes sense or not. That creates a LOT of potential for confusion.
My advice: Go to a REAL gun store and ask them to look at the gun (It would be polite to leave it in the gun case, put it on the counter and talk to them first). Tell them your story and let them check the gun to verify the proper ammunition. If you don't have a gun case, leave it in the car and talk to the counterman.
Before you leave, buy two boxes of their ammo. Their advice is worth it. Or one box and a gun case.
Or, take the gun to a gunsmith. You may get a free verification of the right ammo or for about $25 he might give the gun a thorough examination for safety and shootability (chamber-barrel alignment, cylinder lockup, stuff like that).
Or you could open the crane, read us all the numbers stamped in there (model number, principally) and we could know from the model number. Photographs would help.
But the Gunsmith will be the most authoritative source and has a vested interest in giving you correct information and will tell you that he doesn't know if he doesn't. He has reputation on the line and no ulterior motives.