Sub-class K-5 was 28,000 lb (12.7 tonnes) lighter with 5,800 lbf (25.8 kN) less tractive effort than the infobox figures. ALCO's Schenectady, New York plant delivered builders numbers 46398 and 46399 in 1909, 49201 and 49202 in 1910, and 50844 and 50845 in 1912. Two more were briefly numbered for Maine Central before being transferred to the newly formed Portland Terminal Company, but the remaining six were numbered 161 through 166 in the order built.[1]
Earlier K class 0-6-0s were rebuilt with higher-pressure boilers in Maine Central's Waterville shop between 1913 and 1916 as sub-classes K-6 and K-7. These reboilered locomotives weighing 90,000 lb (40.8 tonnes) with tractive effort of 20,000 lbf (89.0 kN) were numbered 153 through 160. Most were scrapped during the Great Depression and none survived World War II.[2]