Nickle-plated, convex vintage PB&W (Philadelphia, Baltimore & Washington) railroad button is in excellent condition and ready to join your collection.  Button dates from 1902-1918.  Formed by merger of the Philadelphia/Washington line with Baltimore & Potomac RR in 1902 and taken over by the PRR in 1918.  Button measures 9/16" in diameter and is back marked "AMERICAN RY. SUPPLY CO * N.Y."