Ah! I've seen this wing and a description before.

The first time was when I was in England (stopped at Farlow's (sp?)) and picked up a copy of Fly Fishing and Fly Tying Journal (about the only thing I could afford in that store...damn, talk about expensive, but I digress). There were tying instructions for the "Step-over Dun."

And then, Allen McGee had an article in one of our mags a couple of years back, featuring instructions for the Secret Weapon Dun with the same kind of wing.