This image can be found at Dutch correspondent Marcel's web site, MotorParade. This is the 70s era SS50, not the 1960s era Benly SS50, which had a 5 speed gearbox and could hit almost 60mph at 11,000 rpm. The 70s era bike was sold as a moped in most countries, and generally had a rev limiter to keep speeds under 30mph or so. It was succeeded by the MB50, which had road racer styling, solid tri-spoked wheels and a 5-speed gearbox.
Marcel has a lot of images of motorcycle-related collectables, like bike ads, books, and brochures (see below) on his site, as well as a blog that features things like like his personal SS50 that you see at the top of this posting.