Yes it was Reynolds 531: the semi-intact decal was on the top of the seat tube. So at least the main tubes were. Didn't look to see if the fork blades had that one.
While we're on the subject of bike lights; anyone remember (maybe they're best forgotten) the Wonderlights, with the plastic bracket and ball and socket joint? Their rattling sent you insane and they died at the most inconvenient moments.
Found a pic:-
Happy times: heigh-ho!