Have you thought about getting Murph "chipped"? The chip is a little microchip, about the size of a pill, that Tiny's vet placed under the skin on the back of his neck. The chip can be scanned at the pound, or most vet's offices and Tiny's information was in a database that would tell who and where he belonged. Plus, I think the vet had Tiny's medical info in the database too.

I did that with my dog TinyMonsters. He wore a collar, but he was a little Houdini sometimes, and had slipped both his collars off every once in awhile. We used a regular collar with his ID/rabies vaccination tags, and a pinch collar.

The pinch collar would come apart if he shook his head just the right way and the ID collar, depending on how thick his furry neck was at the time, would slide off if he turned his head the right way while on a leash. (we had a little leash "splitter" thingie the connected both collars to each other, so that if one fell off, we might be able to keep him from wandering away after a cat long enough to get the other collar back on)

We figured that chipping Tiny was a good way to be able to get him back if he wandered off. (not a chance, he knew where his munchies were, and didnt like to stray too far away) But, Tiny was an extremely expensive dog, and we were also worried about theft. One of the big reasons we chipped him.