Greg:
Close, but no prize. What you have listed is the scuttle trim screw (and cup washer), which is chrome plated. The screws used to attach the beading to the wing can't be seen after the wing is in place, so a chrome plated screw (and cup washer) would not be necessary.
To attach the beading, the factory used a small round head, self-tapping screw, Triumph Hwdr. Cat. #YA.0183, listed as No.4, 3/8-inch, round head. Most restorers use pop rivets. We used No.4, round head, sheet metal, 3/8-lg, SS.