Doug, I think we have had the discussion about luster before. Note that the coin above will still have luster when you hold it under a light bulb. The reflected light from the circulated areas is dull while that next to the relief (stars, letters, etc.) is brighter as in the image. Since students need to know what luster is/looks like to be able to see it. I have found it is easy to teach someone what an MS coin looks like once they see that the ORIGINAL MINT LUSTER that we apply to coins is very different from the original luster reflected from the metal lampshade at their desk or the unnatural luster from a polished coin.