Winchester stopped producing commercial production of 9mm Luger ammunition when the US entered WWII, although they were already producing 9mm Parabellum ammunition for military customers. Although the Parabellum ammunition was a different load with a different headstamp, Commercial ammunition continued to be produced will into late 1941. This production included both Full Patch and Hollow Point cartridges. By 1941 Winchester had dropped most production of 9mm Luger ammunition with the traditional WRACO headstamp and adopted the military style “W.R.A. 9M-M” headstamp for commercial ammunition (Only a single box of WRACO headstamped 1941 ammo is reported and it is the same date code as the blue & yellow box below - 111 14)
It is interesting that the Full Patch ammunition was packed in the new style blue & yellow boxes introduced after Winchester became a Division of Western Cartridge Company in December 1938, as indicated on the side of the box shown below.
Date code 111 14 (14 Nov 1941)
But the HP ammunition was packed in the older style blue Winchester box that was used in the 1930s.
Date code 61 17 (17 Jun 1941)
Apparently there was a large enough supply of blue boxes that Winchester decided to delay the printing of blue & yellow boxes for HP ammunition. In fact, I know of no examples of blue & yellow HP boxes.
After WWII, In 1946, Winchester began producing commercial 9mm Luger again, but initially using pre-WWII components and the blue & yellow boxes with these boxes being used through 1947.
Surprisingly the Blue boxes from the 1930s showed up again in the 1951 with Western produced, “WRA 9M/M LUGER” headstamped ammunition in both HP and FMJ, but that is another story.
For more info on pre-WWII Winchester production see topic: