This 1915 Folder shows the Trap Grade in 12-gauge "standard" with the 30-inch barrels but one could have 32-, 28- or 26-inch, and in 16-gauge with a 28-inch barrel.
1915 Trap Grade.jpg
The Pigeon Grade only lists 28-inch barrels in both gauges.
1915 Pigeon Grade.jpg
In the paper Winchester called them Trap
Grade and Pigeon
Grade on the firearms themselves they marked them on the bolt
TRAP GUN and
PIGEON GUN.
330325 02.jpg
356173 04.jpg
Hybrid Mode