The Widgeon Duck Club load was probably from the California Powder Company of San Francisco. I've never seen a box.
Relevant reading which might be of interest
Forest & Stream, February 27, 1909
“Small-bore Guns and Loads” discusses 16g and gives it to Hedderly
https://books.google.com/books?id=nE...AJ&pg=PA337&dq
T.H. Grant,
Forest & Stream, December 1915 - 3" shell 2 1/2 Dr. Eq. and 7/8 oz.
https://books.google.com/books?id=lR...J&pg=PA711&lpg
Edwin Hedderly
Western Field editor after July 1910. His first DHE was ordered in 1911.
Arms & The Man 1915
https://books.google.com/books?id=BX...J&pg=PA158&lpg
Recreation 1917
https://books.google.com/books?id=4u...AJ&pg=PA97&lpg
Outdoor Recreation 1919
https://books.google.com/books?id=BX...J&pg=PA158&lpg
Forest & Stream, Nov. 1918 “Keener sport with the 20 gauge gun” Winchester M12 ad
https://books.google.com/books?id=b9...J&pg=PA663&lpg
Threaded Mode