Garth,
Pretty tricky, those guys, eh? I have an '84 Prestige Gran Sport, with those 555 SL stickers on it (I thought they were Reynolds as well when I bought the thing so many years ago!!!).
My guess on the tubing? Tange Prestige! My bike has a fork with the steerer tube engraved "Tange."
Regards,
Chuck Brooks
Malta, NY