Ok, what about this
I just so happened to be peeling through the pages of one of my atlantic salmon fly tying books (Salmon Flies by Poul Jorgenson) and on page 33 on the bottom there is a feather with same coloration and shape. Only difference is near the top which in sean's pic is a tad flat, in this one has a bit of a point. But I know that feathers change in shape depending on where they are at on the body. In the book it's called a "Hen Body Feather". But, shows 5 flies but 6 listings. I can match the rest up. So could it also be Dyed Cock of the Rock??? I knwo it wouldn't be dyed since it was found. But, may have forgotten a feather. Maybe flytyer still has book, or someone else does and can check it out. Looks PRETTY similar. Virtually identicle (just that sean's is a bit more ruffled).
Just an idea. The picture nearly matches identical.
"Good angling ethic is not a monopoly practiced just by fly fisherman" - Bill McMillan