It wasn't a manufacturing unit concern for that model. Potentially Inventive crafting of an ordinary stock. Photos would support to ascertain the appx year your rifle was produced. 44 It had been presented from about 1959-1963. A different defining attribute with the JTSS could it be came using a Winchester https://highimpactrounds.com/product/winchester-xpert-20-ga-2-75in-6-3-4-oz-1325-fps-game-load-25-rd-box/