Thanks, guys,
this fly is tied in what I think is the original form.
The recipe is the original, tied on a hook which may match the shape of the original -
yellow silk, heavily treated in black wax,
coch-y-bondhu hackle,
blackbird(female secondary) wing, starling is a recognised substitute,
I have added a rib as that is the standard variant, where it was not on the original.
This fly works almost everywhere for trout.