What the . . .?

Pictured above are what are called Pigeon Racing Thimbles.
First: Hooray for anything referencing thimbles. Sincerely. Genuinely. YAY!!
Second: I have been trying to figure out what they do with these thimbles in pigeon racing. I've read the Wikipedia article and apparently they have something to do with timing the dear, little birdies, which have some sort of numbered bands put around their legs from when they're pretty much fresh from the egg. I think that when the pigeon arrives at its little pigeon-home-nest-place, pooped from the long flight, its owner (human pigeon-companion, if you will) removes the band and pops it into the thimble-thingy which goes into the pigeon racing clock. Again, I think that's what happens, but I could be entirely wrong (it's happened before). This must be so intuitively obvious to fans of this. . . uh. . . sport. . . that they feel no need to explain it, but I'm dipped if I'm clear on the concept. Seems like one could cheat.
Oh! There are Pigeon Clock Collectors groups and societies! YAY!
I wonder if they have to hear, "You collect what?," all the time too.