Thanks for the input Fred. Thought about tagging you but didn't want to waste your time...especially when you are busy helping others with their $20,000 lucky coins
Thickness at the edge is at least partially a function of striking pressure. A rolled thin planchet struck a little better than normal will have a slightly thicker edge and will look the same as a regular thickness strike The chart shows no examples of a silver coin being struck on SBA stock. It does show the possibility of an sba struck on silver quarter stock which is possible, but it also shows SBA on silver clad quarter stock which is not possible. The reason the actual half dollars struck on quarter stock don't match the chart is because the figures on the chart assumes quarter stock strip that would produce quarters at exactly the spec weight. But since quarters have a tolerance range weight, halves punched from quarter strip also have tolerances. If the strip would produce quarters that weighed at the minimum tolerance weight, a half dollar punched from that strip would weigh 8.66 grams. So the tolerance range for a half struck on quarter stock is 8.66 grams to 9.38 grams. The 8.79 coins shown are light but within the tolerance range.