Willys-Overland / Willys CJ-3A with a default model year should be set as 1949 models, as this vehicle was produced from 1949 to 1953.
(Sources: Willys-Overland Production Figures 1945-1961, CJ-3A Owner's Photos & Serial Number Database, The Civilian Jeep Model CJ-3A / Dating a CJ-3A and a few other websites)

There is also certainly something to do with the Willys-Overland / Willys make name, as the company name was Willys-Overland until Kaiser bought it in 1953.
But information I have found for now about the use of the Willys only name is conflicting: some pre-1953 ads use WO, some others just Willys...