[Researcher]

The first time I've seen something like the Damascus and Twist warnings appear on shotgun shell boxes was the early 12-gauge 3-inch Super-X loads from about 1925 or 1926 --



No mention on this 2 9/16 inch 16-gauge Super-X box of about the same vintage --









The one-piece shell boxes phased in in the 1933-35 time frame, and I've never seen one of those without Damascus and Twist warnings.