I own two mid-1930s Ithaca built Skeet Guns. A No. 4E 12-gauge with all the bells & whistles, which according to Walter was shipped 12/7/36 --
And, a 20-gauge Lefever Model 5 A-Grade optioned up with single non-selective trigger, beavertail forearm, twin ivory sights, and Ithaca bridge trestle recoil pad. It was one of nine similar guns shipped to Bauers Sport Shop 5/1/35.
The guns are both marked S and S on the barrel flats. The 12-gauge chokes measure .009" right and .016" left. The 20-gauge .008" right and .014" left. Both considerably more choke than my Ansley H. Fox Skeet Guns and my Remington pump and autoloader
SKEET choke guns of that era.