This is a Very Special Thai Buddha Amulet. One of the most beautiful I've owned in 30+ years of collecting- I can remember the day I bought it! Superb patina. I believe it is probably from the Sukho Thai era, but I'm not familiar with this type as I've not seen another. I'm reasonably certain that it is at the very minimum 18/19 century or earlier. It looks like it belongs in a museum. I'm digging into the recesses of my collection and putting up the last things I can find that have been with me for decades as I finally downsize as I move into retirement.