Wow, I didn't know I didn't know.
Reason I asked it that of the two lfs we frequent each called what looks to be the same black fish by differing names-telescope & moor. So it is to reason that the arched back of black fish would have the breeding of ryukin? So that is considered demekin? Moors/telescopes tend to have the straighten back?
So intrigued that I probably should get a life!