Here is the Ithaca ad from the July 1926, National Sportsman --
The Ithaca Skeet Special July 1926 National Sportsman.jpeg
I'm guessing that a modified and full choked 20-gauge didn't prove to be a very satisfactory skeet gun!!
Savage cataloged the Fox Skeeter in 1931 --
Fox Skeeter 1931 Retail Catalogue.jpg
For 1932 and 1933 they offered a skeet version of the Trap Grade. For 1934 they offered Fox Special Skeet Grade --
Fox Special Skeet Grade.jpg
Then for 1935, they introduced the Skeet & Upland Game Guns in an SP-/SPE-Grade version --
SP Grade Skeet & Upland Game Gun 1935 retail catalogue.jpg
and a Fox-Sterlingworth version --
Fox-Sterlingworth Skeet & Upland Game Gun 1935.jpg
The Olin brothers must have gotten Winchester going on a Model 21 Skeet Gun in 1932 --
Model 21 Skeet Gun ad Jan. 1933.jpg
as this magazine ad from the January 1933 attests. The Model 21 Skeet Gun is the only one in the 1933 Winchester catalog. During 1933 the Model 12 Skeet Gun and the Model 42 Skeet Gun are introduced, and first appear in the 1934 Winchester catalog.