The shape is a highly unusual one, and happens to be identical to that of a John Wanamaker dept. store, Philadelphia, PA "charge coin," an embossed metal tag which was a forerunner of the credit card, with the customer's ID or account number on it. This isn't a Wannamaker tag (unless it's been reworked) but it might be a "charge coin." I'd try matching up the initials on the front? "C. B. Co."? with listings in old (c. 1900-20) lbusiness directories for major cities in the area where you found it.