[Researcher]

It would likely be 1933 when the 3-inch .410-bore shell was introduced along with the Winchester Model 42. This was in the October 1933 Field & Stream --

.410-bore Skeet Gun, October 1933, Fireld & Stream.jpg

.410-bore Skeet Gun ad October 1933, Field & Stream cropped.jpg

Capt P.A. Curtis may have been a bit off base saying Parker Bros. was first, as this from Ithaca Gun Co. was in the July 1933 National Sportsman --

July 1933, National Sportsman Ithaca 3-inch .410-bore chamber.jpeg