Ivanj is correct. The original Rabco SL 8 was constructed with a wide and flat head shell that formed the entire tonearm except for the block and bearing mechanism that it plugged into.
I owned and modified at least three of these, getting excellent performance for the early 1970's. I mounted the early model we are discussing on several turntables including Thorens, Luxman and Linn while I worked in retail audio.
If you buy one and need information, I remember quite a few tricks, including several ways to improve tracking, and a way to speed up the cue and lift.