RARE All-Clad C3 Copper Test Pan 10” Prototype Experimental Skillet USA Unique

Rare and unusual All-Clad Metalcrafters 10-inch skillet marked “C3 COPPER TEST PAN”  Unlike standard production All-Clad cookware, the underside of this pan is engraved: All-Clad Metalcrafters C3 COPPER TEST PAN 10 In. No. 0652015-01 MADE IN USA  This appears to be an All-Clad test/development piece associated with copper cookware rather than a normally marked retail production pan. I’ve been unable to locate another example with this exact “C3 COPPER TEST PAN” designation or model number.  Features All-Clad’s classic long stainless handle with distinctive cutout and embossed All-Clad attachment plate. The pan has a stainless cooking surface and substantial professional-quality construction.  Condition: Very good pre-owned/test condition. Interior cooking surface is remarkably clean with only light surface marks. Exterior bottom shows scratches, scuffs and handling/use marks consistent with its purpose and age. No major dents or obvious structural damage. Please review all photos closely.  An especially interesting piece for an All-Clad collector, cookware enthusiast, chef, culinary collection, or collector of American manufacturing prototypes/test pieces  Important: I’m describing this according to the manufacturer’s permanent markings on the pan. Because I haven’t located original documentation explaining All-Clad’s “C3 Copper Test Pan” program, I’m not representing this as a specific production Copper Core model. The unusual factory markings are shown clearly in the photos