Here is what I consider an interesting Winchester box…………
Note that the front label date is 11-19……The cartridges within have a tinned 220 gr FMJ bullet with impressed W and an oval tinned primer, indicating manufacture about 1920, many years before the advent of STAYNLESS priming.
So, my idea is that Winchester pulled a ten year old box off the shelf, over-stamped it with the STAYNLESS nomenclature, and marketed it about 1930, assuming the purchaser would not care or know the difference.
With the 220 gr FMJ bullet, this may have been an unpopular loading, even in 1920, therefore never made it to market at the time. The STAYNLESS over-stamps appear on other “slow selling” calibers of the day………6mm USN and 30-03 come to mind.