Hi there, the picture with multiple heads looks like pretty common adorno heads from Central Mexico/Mexico City area. Tens of thousands of them have been found around the Teotihuacan site and a number of other sites. The slightly larger piece might be from Southern Mexico.
The round piece is a Teotihuacan looking head on one side, and what looks like an Aztec calendar on the otherside. That's a bit like finding a Roosevelt Dime on one face and a Roman coin on the obverse face, too much of a gap. I think that piece might be a tourist copy. The little heads could also be copies, but for many, many years it was so easy to find the little heads in fields that no one bothered to make them. That said making them isn't terribly hard, they were mold made back in ancient times and thousands and thousands of molds have been found.
Here is one of mine. Grease the mold, pack in the clay, pull it out, match it up to a piece from mold of the back of the head, smooth the edges, dry it and fire it.
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