XFCZ 297452 at Tulsa, Oklahoma on August 18, 1979.

A railroad reporting mark, officially known as a standard carrier alpha code (SCAC), is a unique two to four alpha-letter code assigned by Railinc. Railinc is a non-profit subsidiary of the Association of American Railroads (AAR). The reporting mark, or SCAC, identifies the owner of a piece of rolling stock. The number that follows is assigned by the owner. The combined code and number are used by railroads, railcar owners and shippers to identify and track equipment. Ultimately this results in billing for movements and shipments.

Reporting marks that end in “Z” have special meaning. These are assigned to trailer owners for use on trailers that are in trailer on flat car (TOFC) service. Other end marks with special meaning are “U” and “X”. Reporting marks that end in “U” are assigned to intermodal containers. Reporting marks that end in “X” are railcar owners that are not common carriers. These may include private car owners, car leasing companies and railroad museums.

Special thanks to Mark Davidson.