These cars came out shortly before MDC/Roundhouse was acquired by Athearn (circa 2005).
Roundhouse sold these cars in 4 car sets (as well as singly). Roundhouse cars come with Rapido-style couplers, whereas the Athearn reissues have magnetic knuckle couplers.
As pictured above, these cars are available with sliding doors (double or single) or plug doors.
50' Pullman Standard box cars like these were built from the mid-1950s through the 1960s.