Winfield was a arms company that bought the majority of the Dutch and other Johnsons in 1953 and marketed them in Canada and the US. They did three mods to the Johnson, the military, the sporter and a scoped sporter. Obviously the military was kept as such, the sporter had a chopped buttend with a hard rubber "Winfield Arms" buttplate on it instead of the square marked parked metal military buttplate and cut off bayo lug. Then the scoped sporter had the chopped butt and drilled and tapped for a scope mount and scope (GOD FORGIVE THEM BUGGAS). On all of them (with exception of the military config ones I think) the Dutch Army or other country markings will have been polished off from their place on the radiator in front of the receiver.
So, telling the Winfield modification means checking the buttplate for the hard rubber one instead of the military metal one, bayo lug or no bayo lug, ground off military markings, and scope mount holes in the receiver.