I am guessing these were paper hulls you saw. Any chance you might recall the brand? The Trojan grade followed the AH Fox Sterlingworth on the market as a economy grade gun, prior to our involvement in WW1- So perhaps these shells you saw predate 1920?
I have read about the special order DHE 20 gauges with 3" chambers and either 30" or even 32" barrels for a Calif. private duck hunting club, so perhaps the 3" 20 paper shells were also of that era?
If I could see the barrels against a good light and "read them"- it might answer the question- as the taper or the lead of the forcing cones found in double guns from that era tend to be different (a tighter angle) than later guns made after plastic hulls and wads, let alone steel shot, became the standard-
Speaking of hulls, my friend- I still have the 100 plus 12 Rem green once fired loads boxed- all I need is a shipping address- so, whenever you wish, send me a PM on that--
They have about 5 Colts in the pending auction at RIA- Feb 19-20. Before I jump into the pond here, has anyone reading this thread ever bought anything (doesn't have to be Colt handguns) from RIA and care to comment- either openly- or to me via PM? Thanks!!
