"Liberation") class; the ㄇㄎ壹 class thus became the 解放1 (JF1) class. The JF1 remained in production until 1960, with a total of 455 being built post-war, numbered JF1 2121 through JF1 2500, and in the 4001−4101 range. Most were built at Sifang (216) and Dalian (187), with Qiqihar Works and other factories producing another 32, in addition to the one unit assembled by the crew of Taiyuan depot in 1958. The JF1 class became the mainstay for freight operations, lasting in mainline service until 1996, whilst some in industrial service remained in operation into the 2000s. At least nine have been preserved, including five in Beijing. Korean State Railway 미가하 (Migaha) class/6000 & 6100 series After the end of the Pacific War, up to as many as 54 Mikai class locomotives which had been on loan from Mantetsu to the Chosen Government Railway (Sentetsu) found themselves in Korea; these were divided between North and South when Korea was partitioned, but the exact numbers are unknown. When the war ended, six Mikai-class locomotives had been assigned to Mantetsu's Rajin depot for operations on the North Chosen Line; these remained in North Korea, where they were put into service by the Korean State Railway. Additionally, China supplied more to North Korea as aid during the Korean War - at least seventy of various JF classes, including JF1s. The 22 engines that had originally belonged to the North Chosen Colonial Railway and that had been taken over by Sentetsu probably all ended up with the Korean State Railway. These locomotives were originally designated 미가하 class (Migaha), and retained their original running number. Later, around the early 1970s, they were renumbered in the 6000 and 6100 series, simply replacing the "미가하" designation with a "6". The following are known to have operated with the Korean State Railway. ミカイ1578 of North China Transport found itself in North Korea after the war, where it became 미가하1578, and then, during the Korean War, was captured by UN forces and taken south for repair. Note that the 6000 series/미가하 class also included the three Mikai class locomotives inherited from Sentetsu, which were a distinct design from the Mantetsu class of the same name. Many were still in regular service in the 1990s, with a few remaining in use into the 21st century. Korean National Railroad 미카1 (Mika1) class An unknown number of the up to 54 Mikai class