Glass fiber has been known for centuries but mass producing it and coating it in resin only dates from the 1930s and 40s. So what is the earliest fiberglass or something very similar could be produced and what would the applications be?
Uh, if you want to stretch a point, you might say the high-silica reeds covered in pitch of Utnapishtim's 'Flood' boat (*) was the first *recorded* resin-mat...
( Yeah, yeah, he's the guy who saved his extended family from a really, really bad river flood, and later told Gilgamesh how it was done. Tale was plagiarised and hyped into the 'Noah' thing... )
*) That 'big coracle' design endured unto 19th century as a river ferry, was actually photographed...