While the Pennsylvania Railroad handled a formidable volume of less-carload-lot (LCL) freight traffic, increasing competition from trucking companies and arch-rival new York Central led to the introduction of dedicated Merchandise Service in the late 1940s. Running on expedited schedules, trains could cover the 900 miles between New York and Chicago in 32 hours.
 
As part of the upgrades, Pennsy launched a major rebuilding program for its signature X29 boxcars, resulting in a larger capacity car with a bigger body mounted on the original underframe, classified as the X29b. These cars served for many years in a variety of Pennsylvania RR schemes including the PRR circle keystone, PRR shadow keystone script, shadow keystone plain, plain keystone, merchandise service (as built) and merchandise service (late). This model is available in these schemes as well as undecorated. The fully assembled model features:

• Correct 10'6" interior height, modernized roof, ends and doors
• Separately applied ladders, grab irons and other details
• Correct size RP-25 metal wheelsets
• Proto MAX(TM) metal knuckle couplers