@chj, for sure it is copper colored, but it seems more likely to be just surface discoloration to me. I'd expect a lower weight and areas of decreased sharpness of the design elements if a clad layer was missing. Here is a link to the page on error-ref for reference:
http://www.error-ref.com/?s=missing+clad
http://www.error-ref.com/?s=missing+clad
"If you climb a good tree, you get a push."
-----Ghanaian proverb
"The danger we all now face is distinguishing between what is authentic and what is performed."
-----King Adz
-----Ghanaian proverb
"The danger we all now face is distinguishing between what is authentic and what is performed."
-----King Adz