This fly is described in Dick Brown's book "Bonefish Fly Patterns". It was designed by Bob Hyde who just happens to run the P&P Bonefish lodge on Exuma
I got the one in the pic from Bob several years ago so its as close to original as you could get. Ask him about the fly, he might even have a couple to give you.
For the fly in the pic, the body is tan wool palmered with a cream hackle. The wing is tan marabou (arctic fox is better). The tail is a bunch of pale blue hackle fibres. You can play around with the colors but many of the crabs down there are very pale tan/cream with either a blue or purple shade on one of the claws. You can play around with colors - sometimes hot orange works down there.
The idea of this fly is it lands incredibly softly and can be cast to spooky fish tailing in very skinny water. You need to squeeze it under water to get it well soaked otherwise it will float! A size 6 is about right. If there is any current, cast it a little up current of tailing fish and let it drift down. Hold on tight