I do not think that Sears ever sold any sporterized military rifles. If the marking you see are on the barrel, I think what you probably have is a rifle that was sporterized using a take-off Sears barrel, maybe ( probably ) from an FN that they sold under their J.C. Higgens name. Is it labeled a Model 51 ( I think that is what they called it ). Even at that, I think, maybe, that Sears abouth the actions from FN, then used High-Standard barrels, so if that is the case, then your barrel was made by High-Standard. Sears also sold Husqvarnas with their house name, along with lots of other variations, especially in .22 rimfire.
Mark