Message:

<p>[QUOTE=&quot;Oldhoopster, post: 2632936, member: 84179&quot;]Maybe it could be due to impurities in the original planchet.&nbsp; If the smelting of the ore was incomplete and impurities were left in the copper it could have shown up in the planchets.&nbsp; In many metals, impurities tend migrate towards the grain boundaries when cooled (although I have no idea what happens in copper).&nbsp; These regions of higher impurities could have reacted faster with whatever caused the environmental damage on the rest of the coin.</p><p><br /></p><p>It might be a stretch, but the metallurgy makes sense.&nbsp; The selective corrosion theory through cracked shellac that was previously mentioned is also a possibility.[/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