Brad,
Pacemaker Graphics were introduced in 1947. The Graflok back was introduced in 1949. The only Graphic on which the Graflok was standard issue was the 2x3 Century Graphic, which has an integral Graflok. Many Pacemaker Graphics, both Speed and Crown, and of all three sizes, were sold with spring backs, which were standard issue; the Graflok was, after it was introduced, the more expensive option. Graflok backs were offered as retrofits for Anniversary Graphics.
Graflex' nomenclature is confusing, but Graflex Inc used it consistently.
The Graflex back has one slider, was native on Graflex SLRs. Late 4x5 RB Super D Graflexes were offered with Graflok backs, and there are firms that will convert 3x4 and 4x5 Super Ds to Graflok.
The Graphic back is what the rest of the universe calls a spring back.
The Graflok back is what the rest of the universe calls a Universal back. As Graflex interpreted it, it has a detachable focusing panel with integral springs; sheet film holders slide in front of it, roll holders replace it. It has two sliders, used to hold roll holders and Grafmatic holders in place. Some universal backs, as on my 2x3 Cambo, must be removed to attach a roll holder to the camera.