My question is a bit difficult to phrase…
Whose is the earliest autograph that is still extant?
[Of course the papyrus is full of correspondence, receipts, contracts etc., but I mean things written by literary greats, generals, church leaders or heads of state.]
Are there verifiable examples earlier than King Odoacer?
I wonder whether there are papyrus documents such as wills or contracts bearing a signature of a less famous person that are even earlier. But I suspect the practice of using a seal was the usual way to guarantee the authenticity of a document, rather than subscribing a signature.
The three complete (or more or less complete) Vergil manuscripts dating from late antiquity have subscriptions by the individuals who prepared them, I believe. I don’t know whether these are thought to be autographs.