What bubba said. And you can run across guns with the "K" at the end of the serial number, as well as guns with a "K" in the barrel channel of the stock but with no "K" in the barrels serial number.
IOW, during the glory years when TC had so many models of traditional muzzies shop proceedures were pretty loose. When parts were gathered from stock to assemble complete firearms or kits, some left the factory with different era (variations) of parts, and some were marked differently as well.