PRR No. 6755 was built in 1930 by the Pennsylvania Railroad in Altoona. It was originally an M1a class but converted along with 38 others M1a class locomotives increasing the boiler pressure from 250 psi to 275 psi. No. 3755 remained in service with the PRR until steam was withdrawn from the railroad in 1957. Originally fitted with lattice tube cow catchers, the M1 front ends underwent similar changes to the K4s, with sheet steel drop-coupler pilots, and swapping the headlight to the top of the smokebox in front of the stack and the steam-driven generator to the front of the smokebox for easier maintenance. This incredibly impressive engine was cosmetically restored (as seen here) by the Museum after receipt from the PRR (8/1969) and eventual donation by Penn Central (12/1979) yet today sits bare today exposed to the elements after having it's asbestos removed. Eventually, the locomotive will once again undergo a cosmetic restoration, though not until a proposed and approved roundhouse is erected to protect her from the elements. The locomotive to the right, tender first is PRR No. 7688, a 2-8-0 Consolidation.