Barry,
I just copied the coin scale off of the internet. I am not sure what year it is from - I was just showing an example of the coin industry's take on it.
I think that it has basically stayed the same over the years, except that they have broken down each of the numerical categories - R8+, R8, R8-. The orginal Sheldon scale from the 1940's or 50's just had R1 through R8 with no subcategories. I think that the scale that you are referencing is the most up to date.
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