I tied a bunch of these years ago. I found them beneath a pile of yellow Woolly Buggers in a box. I always looked at those yellow Buggers, but never selected one to fish. Tonight, I lifted the half dozen or so yellow flies to set them aside. Beneath them were a half dozen of these little gems. Hooks pitted. Flies long forgotten.
What I like about this pattern is the peacock and the darker, tan biots (not the more traditional white biot wing/brown biot tail of a Prince Nymph). The furnace hackle palmered through the peacock body is a nice color contrast. Years ago there was, I recall, a pattern called the Simulator (not Stimulator) that was a worthy stillwater pattern. It was similar to the above except the hackle was trimmed shorter before the biot wing was tied in. It also had the more subdued biot wing and tail. Maybe this was some derivation of that? The fly was tied on a size 10 hook.
It does pay now and then to really dig beneath some of those unused flies you carry year after year, but never use.