Some of the ancient civilizations recorded things in stone or metal which has lasted over the years and can be easily dated. For the most part, the Jewish people used materials which did not last - thus the importance of the Dead Sea Scrolls and the above silver engraving.
In the case of the "scholarly" method described above, before the Dead Sea Scrolls were found, studied and carbon-dated, it was assumed that the book of Enoch was written after 37 B.C. because it contained prophesies about Herod (whose reign began 37 B.C.) but before Christ because it was quoted by the apostles. But carbon dating of the Dead Sea Scrolls (which themselves are copies from another copy or original) dated the DSS copy to about 200 B.C. LOL! So much for "scholarly" method of dating...
That should be repeated more often.
LOL!--that's one of my major complains about liberal Bible scholarship, too :) The Dead Sea Scrolls disproved a lot of late-date theories like that. Another good example of that type of "scholarly dating" fallacy is how liberal scholars long tried to date the Gospels after 70 AD on the grounds of Jesus' predictions about Jerusalem in Matthew 24-25 and parallel passages. Then eventually a fellow liberal Bible scholar pointed out that, um, the language used there is not just in the Gospels, it's also in 1 Thessalonians 4-5, which even liberal scholars date to c. 50 AD. . .whoops! :)
Could you provide citations for your claims. I've read extensively on the Dead Sea Scrolls and I haven't heard this. I'd like to check it out for myself and add it to my corpus of knowledge should it pan out.