Max Gray imported "PRR" round roof single and double door box cars without the "indent" roof. . MG model 241was the 40' single door round roof box car, while 242 was the double double door version (251 and 252 were the 50' cars). Max Gray's August 1963 Condensed Reference and Price List has the 40' single door at $9 and the double door car at $9.45. The detail was sparse by today's standards but with some added parts and a nice paint job one would make for a reasonable stand-in until something better comes along. Max Gray (and successor US Hobbies) cars are frequently found at O scale meets with prices below some of today's plastic models.
PS did you notice the color of the wheel face on the SAL car. Back in the friction bearing era wheel faces looked greasy black - not rust colored as on today's cars.
