One way to make etched data plates for equipment.

Have to try it, I guess. Need to fix the plating supply first.

 

Another explanation of the phenomenon I was seeing is selective etching: if the copper depletes first, then the zinc is visible shortly before it being etched and the whole cycle starting again. There may be some narrow tight voltage range to selectively plate it out. Ideally there'd be some chemical form that can be selectively precipitated out to separate the two.

 

Seems you're right about the voltage part - some brief reading implied the copper would plate out, and the zinc would stay in solution... Most likely, this would mean low(er) current flow.