Standard loads from Outdoor Life Sept. 1922

[Linked Image from photos.smugmug.com]

Note the standard trap load was still 1 1/4 oz.

In 1913 the Interstate Association submitted a poll to trapshooters:
Are you in favor of restricting loads for target shooting to 3 Drams Bulk, or the equivalent in Dense powder, and 1 1/8 oz. of shot?
Frank Butler – “Let me say that the shooter can break targets with a three dram one and one-eighth load if he holds right. Harold Money, who traveled as a professional for years, always used three Drams “Schultze” Powder and one and one-eighth shot.”
https://books.google.com/books?id=fZBBAQAAMAAJ&pg=RA5-PA10&lpg

DuPont began an advertising campaign promoting 3 Dram loads in 1914

In 1919 the Executive Committee of the American Trapshooting Association voted on whether to establish the standard load a 1 1/8 oz. 3 Dr. Eq. The proposal failed.
Arms and The Man, August 2, 1919
https://books.google.com/books?id=TBofKvr1Fi4C&pg=PA377&lpg

It was not until April 1940 that the ATA disallowed 1 1/4 ounce loads.