> with a focus only on books with an ISBN number, the identification system introduced in 1966 So it's not likely to be rare and precious books. It's things which are already in the Library of Congress or its many equivalents. If they're forced by laws to destroy the results of the scans after training on them, as some have implied, that's bad, on the chance there is some actual lost media in there. But if they keep…
SBN started in 1967 in UK (W.H.Smith), official international book numbering (ISBN) is after 1970. Source: https://www.isbn.org/ISBN_history
Also weird that in the space of 5 years, they'd gone from an idea, got national buy in, and then got an international standard sorted.