Following the success of the X23 boxcar (X23 Series Box Car Information for Modelers) design, the Pennsylvania Railroad built over 3,500 cars in a reefer configuration designated as the R7. This fleet of reefers was built between 1914 and 1915 for the Pennsylvania Railroad and its subsidiary lines. By 1922 it had leased nearly the entire fleet of R7s to the Fruit Growers Express Company (FGE), in which the PRR had an ownership-stake. By 1932, the ownership of the entire fleet of cars was transferred to FGE.
Like the X23s, the R7 reefers went through various improvements over time, including 2D-F8 cast trucks replacing the original arch-bar trucks, KD-Brakes being upgraded with AB-brakes, and the lap-seam roof being replaced with a Hutchins Dry-Lading roof.
From 1940 to 1942, over 250 R7 reefers were transferred to FGE subsidiary National Car Company (NX) for use in hauling meat products.
During the early 1950s, a small batch of R7 reefers was leased by National to the Mathieson Chemical Company for use in a dedicated dry ice hauling service.
The R7 reefers lasted in regular service until the late 1950s.
The R7 has been offered in HO scale by Rapido and Westerfield (resin kit).