I had originally posted this to Reddit but the mods removed it and suggested I take it to a rock and minerals subreddit.... which was infuriating. Anyways, this came in a collection of other Mexican arts and pottery. I have not found anything exactly like it online. I actually have a pair of them. I thought it might be for tortillas but it seems small. It's abou 4" across. Any help is appreciated.
Oh that's an interesting idea. But I would expect it have some kind of exit for the grain? I'm not sure.
Smash corn, scrape off, repeat