What Smith's book says, twice. "By far the greatest number of the tablets brought from Nineveh belong to the age of Assur-bani-pal, who reigned over Assyria from B.C. 670, and every copy of what we will term the Genesis legends yet found was inscribed with one exception during his reign." And again: "our only copies in many cases are Assyrian transcripts made in the reign of Assur-bani-pal, in the seventh century B.C."
⭐ The book keeps two dates apart on purpose, and so must anyone using it: the age of the copies we physically have (seventh century BC) and the age of the originals they were copied from, which it argues for separately and at much greater length. Merging the two produces a claim that neither the tablets nor the book supports.
⚠️ The 1915 encyclopedia states it otherwise. Its Deluge of Noah article says the tradition was "found inscribed on cuneiform tablets in Babylonia dating from 3000 BC" and that these "were discovered by George Smith in 1870." Both figures differ from the book by the man it names: the announcement was 1872, and the copies are seventh-century BC. Again, the public-domain text stands as written, and the correction is placed beside it rather than inside it.
Sources: Smith, Chaldean Account, on the date of the copies; ISBE 1915, "Deluge of Noah".