Don't know exactly but what I do know is I flew in a Cathay 747-400 from Paris CDG to Manchester 23 March 1987, so pretty early.
First Cathay 747-400 was delivered 26 September 1988. I suspect that you were on a 747-300, which also had the extended upper deck. The main guide between a 300 and a 400 is winglets on the latter.