I have a 517/16 here next to me. There are no strap lugs of any kind. There is a tripod socket though, I suppose if you're desperate you could use a BlackRapid strap. Lovely camera, a real pleasure to use.
Right now in Spain they're holding the Running of the Bulls,
followed by the Soiling of the Pants, and the Burying of the Idiots.
My 516/16 has lugs, and I found some photos of the 515/16 with them, but I suppose they could be post-factory additions. The 518/16 that I regularly use doesn't---I think the postwar models are expected to be used in their leather never-ready cases.
The 6x6 size is pretty comfortable to carry around in one hand, though. I can fit them in the back pocket of my jeans, but I have a large American butt. :-)
San Diego, CA, USA
The lady of the house has to be a pretty swell sort of person to put up with the annoyance of a photographer.
-The Little Technical Library, _Developing, Printing, And Enlarging_