I have two KarLine Frisco 40' single door boxcars numbered 6250 and 7512 in the Ship it on the Frisco paint scheme that I bought back in the late 60s. At the time I had no idea what the correct numbers should be, but now I believe that there were no four digit numbered 40' sd box cars in that paint scheme. I know that the Frisco had 50' sd box cars with four numbers, but no 40 footers. Even if there were four digit 40 footers, the 7512 falls into the 7100-7799 series 50' sd box cars. Am I correct, or have I just not seen all of the possible numbering sequences? Terry