The origins of this pattern are somewhat unsure. It can be traced back to the Mustad fly catalogue in the late 1920s and is listed in the Museum records as ‘being tied to customers requirements’. Others say it was tied by Norwegian John Sand (1894-1967). This fancy wet was based upon the Silver Doctor salmon fly, and was used for trout and grayling fishing, especially in fast flowing water during the spring flood and was traditionally tied on a double hook in sizes 10 & 12. But after it gained popularity, it became a standard for sea trout and salmon in gin clear water.
This is my interpretation for a single wet trout fly.