I've been told those are quite common, kind of like finding arrow heads up here. They are sacrifices to the gods. When the Azetc's would plant corn or what ever,
the idol for the corn god would be placed in the field to insure a good crop. The next year there would be another, and this was done by each farmer. Then if
you extrapolate for the other gods, you kind of get the idea. That's the total information I have, don't know how true it is. I had a couple of those that had been
given to me, so inquired what they were, and that's how I got my info. One of mine looked a lot like the top row, second from left. I gave mine away a long
time ago.