This is a sort of Chinese good luck token— often called a charm, amulet, or talisman. The characters appear to read Ch'ien-lung T'ung-pao— "circulating coin [or 'current treasure'] of Emperor Ch'ien-lung." Genuine Chinese cash coins of that period date c. 1735-96. However, your find differs from them in that the hole is triangular rather than square; also, it is struck rather than cast as the 18th century coins were. The symbols on the reverse are evidently occult/amuletic.
By the way, there are some collectors who believe this piece is a souvenir item from the Golden Gate International Exposition (world's fair) held in San Francisco in 1939-40, but I have no idea whether that's the case.
