The origins of the fly seems more or less lost in the mist of time, but John Alden Knight is credited with the popularisation of the pattern, which was originally used for brook trouts. The fly might be the work of William Mills & Sons in Canada.
Hook: Streamer - 4-6X long.
Thread: Black (here UNI 8/0).
Ribbing: Oval silver tinsel.
Body: Silver tinsel (here holographic).
Wing: Yellow, topped by red, topped by yellow bucktail.
I mainly use the fly in relative large sizes, but in May, in the salt, a size 8 very sparsely dressed version is a great fly.
If you ahven't got it already, tie some - it's a worthy addition to any flybox.