The Graflok back was introduced around 1950, replacing the Graflex back and Spring backs that had been fitted to the Speed Graphic and Crown Graphics. The Graflok back was an evolution of the sliding bar system of the Graflex back that allowed bulky bag mags and roll film holders to be attached. Ingeniously it also incorporated a spring back with a ground glass focussing panel and pop out hood. While the Grafmatic has the grooves that allow it to be attached via the Graflok’s sliding bars it is just thin enough to slip under the spring back.
Speed Graphic with Graflok back on left and RB Auto Graflex with Graflex back on right
The photo above shows the basic difference between the two types of back. The Graflok back has two sliding bars, one on either side of the back (the chromed metal bars). The Graflex back has one fixed bar and one sliding bar. In the picture above the top brass bar is the sliding one and the bottom one is fixed. As this is a rotating back that depends of course on the orientation of the back.
Speed Graphic with Grafmatic held under the spring back.
The Graflok slides aren’t actually doing anything in the picture above, the Grafmatic is held in place entirely by the spring back. This is very convenient as you can still check focus on the ground glass and then quickly slip a film holder or Grafmatic in place without the need to remove the ground glass first. If you need to use a more bulky accessory like a roll film back or even a digital back then the spring back part can be removed and the graflok slides used to secure the accessory.
Super Speed Graphic with spring back in place
Super Speed Graphic with spring back removed
The Super Graphic and Super Speed Graphic were the final versions of the venerable Speed/Crown Graphic line. The spring back now covered the entire back so that the Graflok sliders are not normally visible. In the picture above the spring back has been unclipped to reveal the Graflok sliders which are an integral part of the camera. The sliders are basically the same as on the Speed Graphic except that the metal is folded for extra strength.
I have seen a few Super Graphics (including my own) advertised as “incomplete – missing back” when the spring back was missing. While this is true, because the Graflok sliders are still there the camera is still perfectly usable if the rangefinder is still working. It is also quite feasible to make a slip in focussing panel, similar to the ones that the RB Graflex SLRs used.