For sale here is an authentic Catskill dry fly by the Dettes - the Coffin Fly.
This fly comes from the collection of a Sullivan County sportsman who, as a kid, grew up around many of the legendary Catskill fly tiers. His uncle was also close friends with many of them. Most of his Dette flies were acquired from another private collector who over the years had regularly acquired his flies directly from the Dettes. Further provenance details will be provided upon request.
Disclosure on all of the "original" Catskill flies here on my website: I did not see these people tie these flies, so I cannot tell you they are 100% authentic. I do however consider my client and his provenance to be absolutely credible. Also, Dave Catizone has inspected each fly in his collection, written up authentication letters for the framed flies (some for sale here), and told me he believes the unframed, individual flies to be authentic as well.