This is a Massachusetts Standard or Clamshell badge. This type of badge was used by most Massachusetts Police Departments between the end of World War I and the present day. This particular badge belonged to Patrolman Owen Coyle. Patrolman Coyle joined the police department in as a Reserve Officer in 1926 and was appointed full time in 1935. He retired in 1957. The badge number for this badge is a small control disk located on the back.