the Qeiyafa Ostracon seems to be, by consensus, the oldest document written in a Hebrew alphabet. From the little I can discern from the writing, the text appears to be written in the Proto-K’na’anite script which was a forerunner of the Proto-Sinai and K’tav Ivri scipts, the latter of which was used throughout the First Temple Period.
However, recent findings - not widely published, perhaps for political reasons - have been made along the newly documented exodus route in today’s Saudi Arabia, among which are an engraving of God’s name, Yahweh, written in Thamudic, which is very closely related to Proto-K’na’anite. Not far from this engraving are others of Israelite symbols, including the Menorah, conclusively proving that the engravings were written by Israelites.
So, an interesting point concerning this matter is what exactly is meant by a Hebrew inscription: is it one written by Hebrews in some kind of alphabet, or is it one written by Hebrews in the fist exclusively Hebrew alphabet?
“There is an old Hebrew book parts of which were found with the Dead Sea Scrolls that said that one of Adam’s sons invented the early Hebrew characters.”
If you believe the above, you might as well believe the idiotic claim made by some rabbis that God invented the Aramaic alphabet Ashurit) for the Jews.
I would think the latter, but that's a very good question. Of the two, which would you say is the archaeologists' primary focus?
"There is an old Hebrew book parts of which were found with the Dead Sea Scrolls that said that one of Adam's sons invented the early Hebrew characters."I didn't say it, write it, post it, or believe it.