This is a new, to me, metal combination that requires some sort of etching, or coloring, or perhaps even etching and coloring, to bring out the pattern.
Today I decided to play with a sample of the Mokume Gane, one that I had sanded and polished to a nice, smooth finish. Here are some shots before the etching. One can clearly see the pattern, but the depends a lot on the angle of the light coming off the piece:
The color differences alone are defining the pattern here, for the most part, although this macro seems to show the copper being a smidgen lower than the nickel silver.
After etching, with ferric chloride:
Now the pattern is easier to notice, since the difference in height between the two metals is greater. I'm not sure that I like the difference in height, but I will reserve judgment until I see the alternative: pattern enhancement by the darkening of the copper. My wife liked it--said it looks like jewelry, so that's one endorsement.