Message:

<p>[QUOTE=&quot;RonSanderson, post: 3159859, member: 77413&quot;]Continuing my proof posts: the 1983-S Proof was the first of the copper-clad zinc proofs. Notice the corrugated surface in the fields and the bubbling below the Lincoln Memorial.</p><p><br /></p><p>[ATTACH=full]810744[/ATTACH]</p><p><br /></p><p>I am curious. Does anyone know whether the corrugated effect is on the surface, or could it actually be the texture of the boundary layer between the zinc and copper? Unless the zinc layer of the planchet was polished <i>before </i>it was layered with copper, then bonded meticulously with copper that was also highly polished, you would expect that interface to be an uneven boundary inside the coin.</p><p><br /></p><p>I would expect the surface to be struck to a mirror-flat evenness, in which case light bouncing from the surface would be uniform and not show any texture.</p><p><br /></p><p>Or, maybe striking a clad coin would cause uneven flow of two metals of different density. Maybe there was some elastic bounce-back after the metals were hammered bu the coin press, and the caused minute ripples to form on the surface.</p><p><br /></p><p>Or, if the outer layer is thin enough, you could get some quantum tunneling of photons through the copper layer to bounce off the interior boundary between the two metals, showing the contours of that.</p><p><br /></p><p>In short, has anyone asked, and answered, why a surface that should be mirror-flat looks corrugated instead?[/QUOTE]</p><p><br /></p>

Your name or email address:

Do you already have an account?

• No, create an account now.
• Yes, my password is:
• Forgot your password?

Stay logged in