The Coptic Crosby-Schoyen Codex, dated to 300 CE ±50 years (and such dating may still be overly precise):
The 104 pages (52 leaves) were written by one scribe over a period of 40 years at a monastery in upper Egypt and are preserved behind plexiglass. The codex contains the first epistle of Peter and the Book of Jonah.This may be the earliest copy of Jonah in Coptic translation, but there are substantial earlier fragments of the Hebrew original among the Dead Sea Scrolls. See the three Minor Prophets scrolls 4QXIIa, 4QXIIf, and 4QXIIg, published by Russell Fuller in Discoveries in the Judaean Desert XV.
The earliest surviving codex (book with bound-together pages) may be the El-Hiba papyrus (Graz, UBG Ms 1946), perhaps dating as early as the mid-third century BCE. See here, here, and here, but with some cautionary comments by Brent Nongbri here.
These details aside, the Crosby-Schoyen Codex is quite important. If it must be put up for sale, I very much encourage the buyer to donate it to a museum, preferably one in Egypt. For precedent, see here.
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