This cut coin pin comes from Panama, and features the image of Spanish explorer/conquistador Vasco Núñez de Balboa. The coin was known as the 1/4 Balboa. I believe this one dates to the 1940's, although the coin was made in .900 silver from 1904 until the 1960;s.
It measures about 15/16 in diameter, the same as the U.S. quarter. This on has a secure pin mechanism and a small attached loop at the bottom, from which something could be suspended.