It's a string of some kind of nuts or seed pods that make a wonderful hollow, "konk, konk" noise when you rattle them together. We brought it back from Mexico last year. Here's a closer look at the nuts, or whatever they are. (They seem to be completely hollow—nothing rattling around inside)
The sound is nice and I like the way they look and feel.
Ray is a drummer and loves all things percussive. He has a really great collection of percussion instruments from all over the place, (remember this find?) so this was something he just had to have. Here's a picture taken in Mexico. I think this is actually the shop in Tepozlan, where we got "the thing." That's Ray checking out the sound of that drum.