The first production class of Pacifics on the Pennsylvania Railroad were the 153 engines of class K-2 erected by the Juniata Shops in 1910-1911, similar in design to a single experimental 4-6-2 of class K-28 delivered by American Locomotive Company in 1907. (A previous K-1 design was never constructed.) The K-2 class had 80-inch drivers, 24x26-inch cylinders, and a boiler pressure of 205 p.s.i. They weighed 278,800 pounds and exerted 32,620 pounds of tractive effort. Their grate area totaled 55 square feet, and they had 3691 square feet of evaporative heating surface and 791 square feet of superheating surface. (When equipped with superheaters, if not so built, they were designated as class K-2s.) In an image by an unknown lensman contributed by Carl Weber, we see No. 3799 posing at Columbus, Ohio in 1938.