This one is up for debate as there’s no definitive answer, however I do feel fairly confident in awarding the ‘best guess’ award (if I had such a thing) to dnaj for his suggestion of the Suzuki GS450/550L. Other points go to Gee S for the GS450T (but that’s not the cruiser variant) and John Schnabel for the GS400 (close, but no cigar).
Here’s what I’ve got, so you can decide if you agree or not. First, an enlarged version of the sign photo: (click to make it bigger)
There aren’t many great photos online of the side profile of a Suzuki GS550L, but here you go:
photo from http://www.suzukicycles.org/GS-series/GS550E.shtml
Some side by side action:
