The top left is how all 15 of the mudhens looked when first built.

In 1906 the railroad converted locomotive #458 to a simple engine by changing it to 17in x 22in cylinders with D slide valve system steam chest and valves. This proved to be a great success and by 1912 all of the compounds except #456 had been changed to simple engines. Additional improvements were made over the next few years including adding a second air pump, flange lubricators, electric headlights, generators and new smoke stakes. In 1918 new larger rectangular tender tanks replaced the old sloped back tenders. Starting in 1923 the D&RG apply Piston valves and Walshaerts valve gear to 11 of the 15 mudhens as well a super heating.