Available for the first time on December 15, 1981, at Shreveport, Louisiana, the 9.3-cent Mail Wagon was the first fractional denomination of the Transportation Coil Series issued. There were 199,645 first day covers cancelled, but there were no first day ceremonies.
The Milk Wagon was intended to pay the third-class, five-digit ZIP code sort bulk mail rate initiated on November 1 and continuing until February 16, 1985. It is a service- inscribed stamp with the words "bulk rate" appearing in the design. Two parallel bars also marked the pre-cancelled stamps.
The Bureau of Engraving and Printing printed 176.79 million Mail Wagon stamps on its Cottrell press. Plate numbers are spaced at twenty-four stamp intervals. The overall tagged collector's version was issued in coils of five hundred using plates 1, 2, 3, 4, 5, and 6. Plates 5 and 6 are much scarcer than the others. The same numbers were issued on the pre-cancelled untagged version as well as plate 8, also quite scarce, but not plate 7.
Jim Schleyer of Burke, Virginia, designed the 9.3-cent Mail Wagon, and Clarence Holbert Bureau of Engraving and Printing modeled the stamp. Gary M. Chaconas engraved the vignette. Gary J. Slaght did the lettering. Both worked for the Bureau of Engraving and Printing.