Each policeman so appointed and commissioned shall, when on duty, carry a shield or star with the words "Police," "Railroad Police" or "Railway Police" and the name of the appointing railroad inscribed on the shield. The shield or star shall be of uniform design. This shield or star shall be worn in plain view when in uniform. The policeman shall also carry, when on duty, an identification card issued by the appointing railroad.   [PL 1987, c. 141, Pt. A, §4 (NEW).]