Unveiled in 1930, the M1a was an improved version of the earlier M1 class. While the M1a was outwardly similar, the most noticeable change was the use of high capacity "coast-to-coast" six-axle tenders. Able to pull heavy freights with ease, they had plenty of steam for speed and were often used in passenger service as well as on important time freights. Models feature powerful five-pole can motor with flywheel, diecast loco and tender chassis, detailed underbody, plated bell and whistle, cab interior, operating headlight, magnetic knuckle coupler on tender, RP-25 contour on drivers and wheels, and Quantum sound system. Locos can be operated on Code 70, 83 and 100 rail, and on minimum 18" curves.