Created by Pat Barnes, a West Yellowstone guide/tyer in the 50's. The PW stands for "Pat's Weighted"; originally a dragonfly imitation, also used as a stonefly and general fish-food attractor.
hook - Mustad 3906 #6
thread - Danville 6/0 black
underbody - non-tox wire
tail - mallard flank
rib - peacock herl (x-small wire re-enforcement)
abdomen - Uni-stretch yellow (original called for floss)
thorax - peacock herl
wingcase/legs - mallard flank
Part 1
Mash down barb, wrap front half of hook with non-tox
start thread, cover underbody; tie in wire and wrap back to bend
measure (shank) some mallard fibers; tie in
tie in peacock and Uni-stretch; wrap the abdomen
twist peacock around wire and rib abdomen (lost the pic - imagination required); prep a mallard feather (even tips make for a neater fly)
tie in with tips facing forward (1/2 body length past eye); wrap back to abdomen