I believe you will find no trap buttplates were used on the Winchester stocks for quite some time. We've discussed that very thing here on a thread a few days ago. Winchester used trapless plates through the summer and into the early fall of '42. It's more than likely this is the rifle that made it to Hurtgen to remain there.
But you don't know that. Gas Trap rifles appeared as late as 1953 at Letterkenny Army Depot for conversion and overhaul.