Just got this beautiful piece from a friend in Mexico. It is made from brass, nickle and copper. Don't think many were made.
If you look at the inner part of the silver colored part, just inside the words "numercion maya", you will see the Mayan counting system. They worked with a base 5 system, at least up to 20. Just googled "Mayan numbers"; turns out the symbol between 1 and 19 is a zero, a sophisticated concept. They did use it as we use our base 10 zero but apparently it was used as a base 20; 20 in Mayan was a dot with the zero symbol below (10 in base 20 is 20). All in all much more sophisticated that Roman numerals.
Numeracion Maya does mean Mayan numbers.
Wonder what is the significance of the 20 faces around the rim. A personification of the numbers? That would be novel. If we assigned a personality to, say, the number 8, what would it be?
The guy associated with the zero symbol looks to be constipated, a lesson there somewhere.