Aztec sunstone
Here’s something that might excite the inner historian or archeologist in you. This disc-like object clearly has a face that originates from either Aztec or Mayan cultures. It’s pretty common knowledge that many relics from their civilizations were round and had hieroglyphs. Maybe the OP had stumbled upon something cool.
They did. This object is a miniature version of an Aztec sunstone, which the people used to might have used to tell time or identify rulers. The markings depict days, months, and suns, but it didn’t function as a calendar. The OP’s grandfather told him not to remove the sunstone when renovating his home. After learning about its origins, he left it where it was.