I recently contacted PCGS to ask HOW they determine "bronze" variety coins versus "brass" varieties of the same denomination coin. I was wondering because I have a 1970 Ten Won coin (South Korea) that's at least MS-63. Midway through the 1970 production-year, the Korean mint changed the metal composition of the planchets for the 10 Won coin from an 88%-12% (copper to zinc) composition to a 65%/35% composition. Now, I know that the metals here don't exactly conform to the exact definitions of "bronze" and "brass," but these are the terms that are used to denote the two different varieties, AND they are the words that PCGS denotes on their slabs when they grade the 1970 Ten Won coin. Here's the response I got from PCGS (see below). Basically, either the person who emailed back to me has no idea how the graders judge bronze versus brass, or it really IS up to the individual grader, based on what they THINK they are looking at. Tell me if this makes sense: Good Afternoon, Thank you for contacting PCGS customer service. It is up to the graders to decide if a coin is indeed a bronze or brass designation. When looking for bronze they are looking an alloy of copper, tin and zinc, with copper the principal metal. It is hard to say exactly what they are looking for as they would need to look at the coin to determine which designation the coin is. Please let me know if I can further assist you. Let me know if anyone out there has any more specific info on how the grading companies determine metal composition... Thanks.
It's a lot easier to tell if they are toned. The earlier coins had a more reddish tone whereas coins struck later have a more yellowish tone. Easiest to compare if you have them side by side.
