Thanks John, that's what my gas cap looks like as well.
I don't think the wing ones were on the 58, 59 or 60 birds.
The cap seems to fit a little loose and I think that relates to the vent ability.
The gold colour ones with the wings are a vented cap. I understand that the vented gas caps came out latter. Possibly in 61?
I'm guessing John's picture is closer to the original. Saved me buying one!