Originally built by Baldwin in 1917, the Reading's class M1-sa 2-8-2s were rebuilt in the company's shops in 1924 to enhance their performance, principally by removing some boiler tubing to reduce the heating surface and improve the flow of firebox gases. At the same time their cylinder volume was enlarged. As rebuilt, the M1-sa group had 25x32-inch cylinders, 220 p.s.i. of boiler pressure, and a 61½-inch driver diameter. Their large Wooten firebox, intended originally for cooler-burning anthracite, had a grate area of 108 square feet. Their evaporative heating surface totaled 3803 square feet, with 993 square feet of superheating surface. They weighed 334,425 pounds and developed 60,813 pounds of tractive force. Apparently these Mikados worked in passenger service, as shown in this postcard view of No. 1715 at the Jersey City terminal of the Central Railroad of New Jersey. The date is not given but the photo is attributed to R. D. Fullerton.