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<p>[QUOTE=&quot;Conder101, post: 3008984, member: 66&quot;]The strip is created from three ingots of metal, two of copper nickel and one of copper. These are stacked and bonded together using very high pressure rolling (Before rolling the surfaces of the ingots that were going to be in contact with each other our ground very smooth and thoroughly cleaned. This is done to provide maximum contact between the surfaces during the rolling.) After the ingot layers are bonded, lower pressure rolling is used to finish rolling it out into strip. In theory, the entire surfaces between the layers are firmly bonded together. But sometimes there will be areas that do not bond together properly. If the planchet is cut from one of these areas the outer layer is not well bonded to the copper and may fall away either before or after striking. If the planchet is cut from an area that overlaps a well bonded area with a poorly bonded area you get a clamshell lamination. Whether the outer layer falls away before or after striking the final coin with a missing layer will be significantly, roughly 25%, underweight.</p><p><br /></p><p><br /></p><p>Weight is the key, but simply because the layer is missing. Copper and copper nickel have nearly identical densities and specific gravity. Specific gravity of copper is 8.96, nickel is 8.90, coppernickel is 8.92.</p><p><br /></p><p><br /></p><p>That would be correct but coins with a missing clad layer are almost never made from just two layers of material rolled out to the proper dimensions. They are almost always from a planchet that had all three layers originally and the outer layer from one side has fallen away.[/QUOTE]</p><p><br /></p>

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