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Message:: [QUOTE="physics-fan3.14, post: 3959610, member: 19165"]I mean, it perfectly well could be a Rockwell hardness test. The divot is about the right size. The cent is a known composition and widely available. It's quite plausible that a material's lab could have their students test a dozen pennies and write a report. That seems like a very easy test for a science class (in fact, I did exactly this experiment in college). Often when we see these sorts of mutilated pennies we attribute them to malice. But we forget that the "penny" is a well standardized unit of known weight, measure, and composition. Science classes are built around testing these sorts of things, to expose students to various testing methods. There are literally billions of cents minted every year, and they make an easy and cheap source for a science class. Also..... I'm not sure some of you folks know what a "Rockwell" test is. This is definitely not something the mint does on manufactured coins (it might do it during testing.... but not a routine test on production coins). The "Rockwell" test is a test of the hardness of a material, rated 1-10. It uses a punch to make a divot in a material (Rockwell hardness uses a round punch as shown here, Brinell uses a cone shaped punch). Something like lead will be a very soft material and make a very large punch; something like diamond is a very hard material and will leave almost no trace at all (rated 10). A copper cent is a generally soft material, and will thus leave a fairly large divot. Thus, in my opinion, it is highly plausible that the marks shown here are Rockwell hardness tests. However, they are of course post-mint damage and utterly worthless. It's just important you know what the OP is talking about.[/QUOTE]

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