No. 4387, a somewhat improved version of Bay State Street Railway semi-convertible No. 4175, is one of 200 cars built for the Bay State Street Railway by the Laconia Car Co. in 1918. it has large platforms and extremely large three sash windows, of which the lowermost drop into pockets in the sides. The frame is of composite steel and wood construction and the car is equipped with both transverse and longitudinal seats, having been designed for operation on both city and suburban lines. They were widely used throughout the vast Bay State system.