The illustration,s of Stub Damascus seen in both Akehurst,s and William Greener,s books do not show a uniform pattern as evident in your post. When you have the Akehurst book available, you will note that there is no uniform pattern in the illustrations of Stub Barrels.This is because the aglomeration of the nail stubs in the ball feeding the ribbon are in a random aray. Hence you see a mottled pattern on the finished barrel surface.

Roy Hebbes