For those of a non engineering background, often the lack of a correct name hampers a search for what you are actually looking for.
Eventually i discovered those fancy convex & concave knurls on scientific instruments of yesteryear are known as 'Rope Knurls'
Does anyone still make these i wonder??
I guess a good hobby engineer could probably make his own,silver steel tooling should be good enough for brass?~ i'll have to pass on that for now.