Reply to Thread

Message:: [QUOTE="desertgem, post: 2123133, member: 15199"]I think the mantra of color progression might also be looked at a little more. Yes, color depends on the the thickness of the thin diffraction film of toning/corrosion of the coin metal. To progress in color, there has been a continuous increase in thickness from the most toned areas to the least over time. This is easy to assume if the coin has been in a 'toning book' where sulfur containing paper has held it in place by the edge, setting one side down in old wood/felt coin cabinet drawers, or even toned within hard plastic holders with leaky seals, the color change would be progressive as each layer increased in thickness from single direction.But if the toning contaminant was hitting the surface equally, the color would tend to be caused by less of a variation, and more grouped around a specific range, and if the flow direction was changed for random periods of time, or the coins position was changed there could be areas where the progression was not in specific order. Color progression is an excellent tool, probably higher than 80% effective, but that is where experience and knowledge can increase it, such as observing the edge of the coin (as an area that AT makers often can not control toning ) for progressive  color coins, as the edge of album tones coin should be most advanced there, and as Lehigh and other do, look at thousands of examples.[/QUOTE]