It looks like a material variation of John Atherton's HALF STONE. Atherton's original recipe is:
tag: Oval silver tinsel
tail: G.P. crest and unbarred woodduck
Body: Rear, yellow dubbing (thin);
Front, black or brown dubbing
rib: oval gold
hackle: furnace, or black
wing: fox squirrel tail
As can be seen from the Atherton original pattern, the fly you pictured has substituted yellow yarn (I would use antron or Z-lon) for the G.P. crest and leaves out the unbarred woodduck in the tail. Otherwise, it is the same fly.
John Atherton fished the Marimichi a lot for salmon and used this fly in his fishing. I'm equally sure that guides and others copied the fly. It was considered to be an indispensible summer fly at one time.