Hook - Mustad 3906 Wet or 94840 Dry size 14
Thread- Uni 8/0 Black
Tail - Brown Hen Hackle
Body - Muskrat (guard hairs removed)
Collar - Brown Hen Hackle
The lowly Muskrat. My gateway drug into the world of Flymphs and Soft Hackles, and still my favorite pattern.
The fly in the picture is tyed on a Mustad 94840, size 14, but I tie them down to 20's aswell. I dont know what hook the original was tyed on, but I do well with both the wet and dry hooks. I tie an Olive Muskrat, and an Orange one aswell. These two are tyed with rabbit instead of Muskrat. When my non fly tying buddies would bum flys off me, they would ask for either the Orange or Olive "Muskrat" and the names just stuck with me.
.............oh well..... 
...........i was recently told they are not the same animal...........and i believe you have it exactly right Ray. 