What you have here is a Rose Farthing of King Charles I of England. This particular type of coin was struck from 1636 until 1644. http://www.wbcc-online.com/new-releases/rose.html http://www.britishfarthings.com/Royal/2/Charles_I_Rose.html
@Bradley Trotter beat me to it. I am pretty sure some of these have been found in archaeological digs at Jamestown, Virginia, here in the States. That piece looks to have spent some time in the ground as well.
I’d love to get my hands on one of these. I’m descended through my maternal grandmother from John Pym, one of the five members of Parliament whom Charles I tried to arrest in 1642. That’s the origin of the ritual where before the Queen’s Speech, she has to dispatch the Gentleman Usher of the Black Rod to summon the House of Commons, whereupon they slam the door in his face and make him knock to get in - meant to assert the Commons’ independence from the monarch, who herself is not allowed to enter.
