Do you mean how do the grading companies assess the scratch aways?
If so, I would look on eBay for as many graded 1964 cards as you can (sold auctions too), and examine the ones with back scans to see if you can detect a pattern. In other words, if PSA 7s and 8s have scratched backs, it most likely means they don't detract for it.
Last edited by JollyElm; 03-10-2022 at 08:34 PM.
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