Identification Of Coin

It is not an actual coin. It is a "Masonic shekel", used in the rituals of the Royal Arch degree of Freemasonry. In this branch of Freemasonry, when a candidate Mason graduates or is "made mark" in this degree, they are assigned (or select for themselves) a secret mark, similar to the secret marks that mediaeval stonemasons used to use to identify their work, and are given a token on which their secret mark can be engraved. The token can then be used as a kind of identity disk at future Lodge meetings.

See the "GS" monogram stamped into the centre of the circle in your bottom picture? That's the secret mark of the Mason that this token originally belonged to. "57" isn't a date, it's the branch number of the Lodge that issued the token. The keystone symbol surrounding it with the mysterious letters "KSHTWSST" is the badge of Royal Arch masonry, often found on Masonic shekels and Masonic pennies. If you want to find out for sure what those letters mean, you'll have to join the Masons - it's one of their super-secret secrets. Or you can just Google it (hint: you might need to Google "HTWSSTKS" as well).

The design on the other side is rather crudely copied from an ancient Jewish shekel.