The Boston & Maine received five 4-6-2s from Lima Locomotive Works in 1934 in class P-4a. They had 80-inch drivers, carried 260 p.s.i. of boiler pressure, and had cylinder dimensions of 23x28 inches. Weighing 339,200 pounds minus tender, they developed 40,918 pounds of tractive force which (according to one source) a trailing truck booster raised to 52,800 pounds when starting. (For other specifications see the commentary for No. 3716.) When Lima delivered a second group of P-4s in 1937, the railroad sponsored a contest among elementary and junior high school children in communities along its lines to name the locomotives. No. 3710, the first member of the class, received the name Peter Cooper after the man who created the pioneering Tom Thumb steam locomotive in 1830. As this 1934 builder's photo reveals, the P-4a class was delivered with a skyline casing which was later removed for ease of maintanance.