The above shotgun, early Winchester import, 2 barrel set, both numbered to the gun, one being a single barrel trap. Non-selective trigger and from my recollection of ones i've had before fires the bottom barrel first. The single barrel is an upper. So how do you go about firing the upper barrel only? The gun came with 2 complete trigger groups. The spare trigger group obviously fires both barrels. The one that's in the gun, I've not removed to look at yet.

Roger