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<p>[QUOTE=&quot;Rob Woodside, post: 7497309, member: 96187&quot;]Thank you very much for a very helpful thread.</p><p><br /></p><p>Please don&#039;t confuse the surface marks called &quot;flow lines&quot; with the actual flow of matter. This is like looking at the surface of the ocean near a beach and calling the lines of wave crests&nbsp; &quot;flow lines&quot;. Those obvious lines certainly do not describe the flow of water in the waves.</p><p><br /></p><p>So are these surface marks caused by die wear or by ripples of fluid metal flow during striking, much like the lines of wave crests on a beach?</p><p><br /></p><p>If it is all die wear then the characteristic &quot;cartwheel&quot; chatoyance of mint state coins is die wear! My predjudice is that this is nonsense and that any groves or ridges visible under ten power are certainly not surface ripples frozen from the time of striking.</p><p><br /></p><p>Chatoyance is a diffraction and interference effect. Diffraction is the ability of waves to bend around edges. (Newton knew that light was a particle because the edges of shadows were sharp and sound was a wave because you could hear around corners.) So whether you have a ridge or a groove light can bend and reflect from where it shouldn&#039;t. If you have a lot of parallel groves or ridges then the reflected diffracted rays can constructively interfere producing the bright diffraction streaks of chatoyancy that move around as you play the coin in the light. It is important to realize that these diffraction streaks are perpendicular to the edges that produced them.</p><p><br /></p><p>Currently I&#039;m trying to understand MS (Mint State), PL (Proof Like or Proof Lustre), and SP (Specimen Proof) (Thanks John) Canadian silver dollars. The MS were supposed to be one off commercial stikes. The PL were supposedly double struck at possibly higher pressures and the SP were multiply stuck at even higher pressure. Does any one have any references on this? The delicious liquid suface of SP is obvious. The chatoyancy of any MS coin makes that obvious too. The PL have no chatoyancy but sadly neither do some MS coins and the relative frostyness is supposed to sort the PL from the diffractionless MS coins. So why are some MS coins not chatoyant? If the microscopic flow lines were frozen ripple marks in the metal, shouldn&#039;t they be in all MS coins produced the same way? A simple explanation would be that all flow lines of any magnetude are the result of die wear![/QUOTE]</p><p><br /></p>

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