I have not looked in my Gun Digests - they are a good source of information but not the best source. However, I have a Winchester 4-page advertising flyer with code “10-52-10” which I believe means it was issued in October 1952, introducing the then-new Winchester Model 70 Featherweight rifle and the then-new .308 Winchester cartridge. The date October 1952 squares with a Winchester price sheet I have from September 26, 1952, that lists the .308 Winchester cartridge available in 110 grain Soft Point Super Speed (Index W3081), 150 grain Silvertip exp. Super Speed (Index W3082); and 180 grain grain Silvertip exp. Super Speed (Index W3083).
This price sheet has an appended factory “pink slip” announcing that “The attached list shows the new and old Winchester Ammunition Symbol Numbers.” In short, it introduced a new code system as of September 26, 1952. Under the “Old symbol” column on the price list, there are no old symbols listed for the .308 Winchester, indicating to me that this was the first factory price list that this cartridge appeared on. It is the only cartridge, RF, CF or shotshell, that is listed without an old product symbol.
The four-page brochure on the Model 70 Featherweight and the .308 has a layman’s history of the cartridge included in it. It is an interesting document. It shows the same three loadings with the new product symbols, by the way. The recommended list price for the ammunition was $3.70 per box of 20 rounds, and the recommended price for the Model 70 Featherweight was $120.95 with either a Monte Carlo Stock (Product code G 7060 CN) or a standard straight comb stock (Product code G 7020 CN). I’ll take two of each, thank you!
Hope this is of some help and interest.