I took the cup to a well-regarded instrument repair company here in town. The owner seemed to know what he was talking about and was rather intrigued about possibly repairing a magic prop.
However, after examining the cup, he found another split I hadn't detected before. :(
He said that while he believed he could repair the splits, I would still be left with a visible line where each repair would be. He was also concerned that this would stand out when compared to the other two cups. In short, as much as he would love to repair the cup, he recommended against it.
Bottom line: I've decided not to attempt a repair (especially now that there is a second split in the cup). Curse you, Jeff Busby! :mad: (To be fair, the cups are 20+ years old, and are certainly still perfectly functional. Yes, I know, it's what you do with the cups, not the cups themselves that matter. Still...).
So, perhaps it is time for a new set of cups? I did contact Brett Sherwood upon Mr. Riser's suggestion. Mr. Sherwood says that his brass cups are properly annealed and are thick walled so they are less susceptible to cracking.
I really like the golden look of brass, but don't know if I'm willing to risk spun brass again.
Alternatively, I could learn to love copper, especially if the smooth copper Sherwoods are in view. (Is copper as dent resistant as brass?).