This is my first time posting. I'm seeking information about a Colt Police Positive Special with Railway Express markings. Serial number on the pistol is 516636. The book by Wilson dates it to 1949. The finish is the hot dip blue, but the cylinder grooves, grip strap and trigger guard have the matte blue. The backstrap has the following marks: RY EX AGY which I believe stands for Railway Express Agency. The grips are the dark brown plastic with the Colt logo at the top. The caliber is 38 Colt NP. First is the gun correct. The large Blue Book claims no production after 1946, and that all had checkered wooden grips. Second are cartridges available? Thanks for any help.