japan made metal thing

Hi! I found this in San Francisco. I was curious what it is and if it is work anything. It is about 4" x 4" and the material feels like ceramic. Thank you in advance for the help!

This was in some of my Dad's military items that he had from WWII. A loose translation of the Asian (Japanese & Chinese) given to me by a Japanese friend. Big time hunter or Hunting big time. The reverse has no markings or inscriptions. The pin has a screw back.