Unwrought copper-zinc alloys (brass) classify under 740321, copper-tin alloys (bronze) under 740322, and other copper alloys not elsewhere specified under 740329. Pure refined copper — regardless of form — falls under the 740311–740319 subheadings. The alloy composition, confirmed by mill certificate or chemical analysis, is the determining factor.

Importers generally present a producer's certificate of analysis showing copper purity (typically 99.99% Cu for Grade A cathodes), the LME or COMEX registered brand mark if applicable, and a commercial invoice referencing the cathode form. Customs may request assay reports or registered brand documentation to confirm the article meets the refined copper standard rather than classifying as unrefined copper under heading 7402.