“Which ones?”
Probably the West Syriac ones, at least some of them. The Didache speaks of them. I think its likely that the anaphora used by the Maronites might be one, or at least very close. The one we use on most Sundays is from the 4th/5th century, but is taken from the West Syriac ones so would be recognizable if not exactly the same wording. This isn’t as remarkable as you might think. If I were to attend a Maronite Liturgy, or a Roman Catholic Mass or a High Church Anglican Liturgy, or the Liturgies of ++ Mark or James, I’d recognize their anaphorae immediately despite the fact that they are all different from the ones I hear. They all come from the same sources.
So about the 5th. cen. is the earliest known for sure.
“Our first Syriac documents come from about the end of the fifth century (”Testamentum Domini,” ed. by Ignatius Rahmani II, Life of Severus of Antioch, sixth century).”
Catholic Encyclopedia