Joined: Nov 2010
Posts: 15,315
Likes: 903
From: Tixkokob, Yucatán, México
Bikes: 79 Trek 930, 80 Trek 414, 84 Schwinn Letour Luxe (coupled), 92 Schwinn Paramount PDG 5
You might try dating the Sturmey Archer hub, to get in the ballpark. I don't know the particulars of that but somebody here does.
Edit: The components might also have date stamps on them.
Welcome to the forums.