class and numbered 6700 through 6733. A further forty, numbered 6734 through 6773, were added in 1934 and 1935. Though nearly identical to the Mikai class locomotives, the Mikana class were equipped with shorter tenders, as the Manchukuo National used shorter turntables than Mantetsu. Under the unified classification scheme of 1938, Mantetsu's Mikai class and Manchukuo National's Mikana classes were merged as the Mikai class; under this system, Mantetsu's locomotives became ミカイ1 through ミカイ70, whilst the Manchukuo National units became ミカイ501 through ミカイ574. Mantetsu Mikako (ミカコ) and MNR "New Big Mika" (新國大ミカ) classes After Mantetsu transferred its Dekai-class locomotives to the Manchukuo National Railway, it ordered an improved version of the Mikai class locomotives as a replacement. The new type, called Mikako (ミカコ) class, featured a combustion chamber firebox and a feedwater heater, and eighteen locomotives, built by Kawasaki, Kisha Seizō, Hitachi, the Shahekou Works, and the Dalian Machine Works, were delivered between 1935 and 1937; these were numbered ミカコ1570−ミカイ1587. Like the Mikai class, these used a Type A superheater, but experimentally, ミカコ1577 and ミカコ1587 were fitted with a Schmidt Type E superheater. A further 243 were built between 1938 and 1945. The Manchukuo National also ordered the new design, where it became the mainstay of the MNR's locomotive fleet - the 709 units delivered accounted for over half of the 1,393 locomotives of all types rostered by the Manchukuo National. Known as the "New National Big Mika" (新國大ミカ) and grouped in the Mikana class, they were initially numbered ミカナ6774−ミカナ6899, ミカナ16700−ミカナ16717, and ミカナ16737−ミカナ16738. Twenty units, ミカナ16718−ミカナ16736 and ミカナ16739, were built for the Manchukuo National but were diverted to the North China Transportation Company prior to delivery. In addition to the 146 built between 1935 and 1937, a further 563 were delivered to the Manchukuo National by the collapse of Manchukuo in 1945. In the unified classification scheme of 1938, Mantetsu's Mikako class and Manchukuo National's Mikana classes were merged with Mantetsu's Mikai class as the Mikai class; under this system, Mantetsu's Mikako class locomotives became ミカイ71 through ミカイ341, and the MNR's units became ミカイ575 through ミカイ1283. The North China Transportation Company, a subsidiary of Mantetsu established in 1938 to operate railways and busses in the territory controlled by the Provisional Government of the Republic of China (part of the collaborationist Republic of China from 1940 to 1945), received twenty "New National Big Mika" type locomotives that had been built for