[Linked Image from i.imgur.com]
1934 20 gauge Trap/Skeet

As a Skeet shooter and a fan of the Model 21, I’m trying to understand the logic behind this early Trap/Skeet.
Why the overlap between this gun and say the “New Fangled” Tournament Skeet (1933-1935)
Dimensions are pretty much identical as is its’ configuration. Other than the Trap forend (longer and taller) what’s the difference?