Another indication of 1935 manufacture is the absence of the term non-mercuric with the “Non-Corrosive Priming” description. Western was still using at least some mercuric, non-corrosive primers through January 1942 but was producing non-mercuric, non-corrosive primers by Sep 1939. In a 1 November 1944 Western letter, one of a number in the possession of Pete DeCoux, Western 7mm Mauser lot numbers 2KN81 (18 Dec 1935) and M8SK01 (10 Sep 1941) were described as having “mercuric, non-corr. primers when they left the plant.” 6mm Mann. Scho. lot number 47TA42 (24 Jan 1942) was also described as having mercuric, non-corrosive primers.
Pete also has a box of Western non-mercuric, non-corrosive primers lot number 84PK6 (6 Sep 1939), and I have boxes of presumably Western primers lot number 90RE22 (22 May 1940) with WINCHESTER STAYNLESS labels of the 1939-style (Division of Western Cartridge Company).
What I find most interesting about these letters, however, is that they contain the statement “Since the end of May, 1942 we have not been permitted to manufacture any sporting ammunition or components due to the War production board.” Yet some of the lot numbers discussed ARE commercial production after May, 1942: such as 270 Winchester lots D8UK4 (4 Sep 1943), and 37VE21P and 47VE91D (12 and 19 May 1944). All post-Jan 1942 lot numbers discussed had non-mercuric, non-corrosive primers.