Gleaning data about members of the Missouri Pacific's MK-63 class of Mikados can be confusing. The 1251 subclass of the MK-63 group came from Baldwin Locomotive Works in 1913-1914 as Nos. 1251-1280. Over the years, however, the railroad rebuilt these 63-inch-drivered engines changing their specifications and appliances so that the various examples differed one from another. In rebuilding, the Sedalia Shops converted many of the 1251 subclass from coal to oil, including No. 1274 shown here, and replaced the original fabricated trailing truck with a Delta trailing truck that incorporated a booster raising the engine's total tractive effort to 65,190 pounds. Cylinder dimensions were reduced from 27x30 to 26x30 inches, and boiler pressure was raised from 170 to 200 p.s.i. Sources indicate that No. 1274 was not given the Worthington feedwater heater the others in the oil-burning group received, but from the box-like projection behind the bell in this photo it does appear to have the Worthington type. Heating capacity specifications for the oil-burning group are given as 56½ square feet for grate area, 3521 square feet for evaporative heating surface, and 770 square feet for superheating surface. Members of the 1251 subclass remaining on the MoPac roster were retired between 1949 and 1955. No. 1274, looking fresh out of the shops, appears at St. Louis in a 1935 photo by R. J. Foster from the Roy F. Blackburn collection, acquired from an eBay seller.