|Soo Line flat car #X54385 was acquired by Mid-Continent in May 1984. It arrived as the boom idler car with Soo Line steam crane #X-81. Pullman Standard Car Manufacturing Co. built one hundred of these 55 ton capacity, general service flat cars at its Michigan City, Indiana works and delivered them to the Soo Line in December 1939. The cars were built in Pullman Lot No. 5600 and numbered 54301 through 54499 (odd numbers only). At some date, presently unknown, the flat car was assigned to work service as a crane boom idler car. There is no evidence that the railroad ever renumbered it into its work service series.