When the Wabash Railroad ordered 50 Mikados in 1925 from ALCO-Schenectady, five were to be built with three cylinders. These became class K-5 and were numbered 2600 to 2604, while the two-cylinder locomotives became class K-4. The idea behind the three-cylinder locomotives was that they promised to deliver less slack when starting a heavy train and more uniform acceleration, what might lead to less consumption. The cylinder layout was very similar to the Louisville & Nashville No. 1999 and the Missouri Pacific No. 1699.

All cylinders had a diameter of 23 inches, but a different stroke and a different type of valve gear. While the outer ones were controlled by Walschaerts valve gear and had a stroke of 32 inches, the inner one had Gresley conjugated valve gear and a stroke of only 28 inches. Like the K-4, they had the same boiler, a Schmidt type superheater and a duplex stoker. It was quickly found out that the inside cylinder and valve gear were harder to maintain than they were supposed to, and all locomotives were put into storage after a short time. In 1943, all five were rebuilt into the two-cylinder class P-1 4-6-4.