This is a coal-burning, class M1b 4-8-2 steam locomotive that was built by the Pennsylvania Railroads Altoona Works in 1930. It is on display at the Railroad Museum of Pennsylvania in the town of Strasburg. Info. from rgusrail.com: 6755 is an M1b class Mountain type locomotive (4-8-2) built as an M1a by the Pennsylvania Railroad at its Juniata work shop in Altoona, Pennsylvania in 1930. The prototype for the M1 class was built by the Pennsylvania Railroad in 1923. After exhaustive testing, the company then ordered one hundred and seventy-five of the class from Baldwin and a further twenty-five from Lima in 1926. In 1930, twenty-five M1a class locomotives were ordered from Lima, fifty from Baldwin and twenty-five built at Altoona, Pennsylvania by the Pennsylvania Railroad (including 6755). These featured one-piece cast cylinder saddles with inside steam delivery, Worthington feedwater heaters and two air compressors. Thirty-eight M1a locomotives were subsequently converted to class M1b with higher-pressure boilers (from 250 pounds per square inch to 275 pounds per square inch) and firebox circulators. 6755 was converted in 1944 and remained in service until steam was withdrawn from the Pennsylvania Railroad in 1957. The M1 was the largest steam locomotive to operate on the Pennsylvania Railroad system and, although designed for dual service, it was used mainly on fast freight services. The M class weighed 385. 000 pounds, although the M1 and M1a delivered tractive effort of 64. 550 pounds, while the M1b delivered 69. 700 pounds. The M1b weighed 391. 000 pounds, 271. 000 pounds on its 72 inch drivers. With 27 inch x 30 inch cylinders, a 69.9 square feet grate and 397 square feet firebox, total heating surface was 6. 332 square feet including 1. 630 square feet superheating. 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 fr ont of the stack and the steam-driven generator to the front of the smokebox for easier maintenance. A wide variety of tenders were mated with M1 locomotives. All had scoops to pick up water from track pans and, at the rear, were fitted with a doghouse for the head-end brakeman on freight trains.