I don't believe there ever were .38 WCF in Copper. Very few center-fire cases of any caliber were Copper. Often chemical cleaning of brass will leach the Zinc from the surface leaving the brass red and appearing to be Copper. If you are willing to damage one try a stroke of a file across one of the cases and I will bet the filed area will be brass colored.
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Gunsmithing since 1961
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