there are some members that know a lot more about it than me
but I do not think the missing data has anything to do with grades-
the gaps occur mostly in ranges - blocks of numbers some quite large - and many of the numbers not in the book still have info available for letters -
So I think it was just a matter of what was available to the author when he made his lists
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"If there is a heaven it must have thinning aspen gold, and flighting woodcock, and a bird dog" GBE
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