Yes. In general -- there are exceptions -- film holders that fit one won't fit the other.
Originally Posted by Californiakid
Graflex Inc was a company; Graflex Inc is the last incarnation, it began as Folmer & Schwing. Graflex is a brand. Within the Graflex (the company and brand) product slate Graflex cameras are all SLRs with focal plane shutters. The Graflex back was introduced I don't know when (early 20th century) and was used on Graflex SLRs. Graflex backs have one slider, a lip opposite the slider that one edge of the film holder slips under and a lip at the insertion side of the gate. This lip fits in a groove in the film holder. Graflex SLRs rarely have ground glass focusing panels that sit behind the shutter. However, Graphic press cameras (read on) could be ordered with Graflex backs; these backs have focusing panels that are attached and detached like film holders.
Graflex the company made a number of camera types in addition to Graflex SLRs. These include view cameras and press cameras. Graflex' press cameras were called Graphics. Early ones (up to the next-to-last incarnation) all have focal plane shutters, are called Speed Graphics. The next-to-last incarnation (Pacemaker Graphics), introduced in 1947, expanded the line to include press cameras with no focal plane shutter (Pacemaker Crown Graphics, usually called Crown Graphics) and with focal plane shutter (Pacemaker Speed Graphic). All of the SLRs and press cameras have wooden bodies. The last press camera, the Super Grapic, has a metal body.
In 1949 Graflex Inc. introduced the Graflok back. Two sliders, removable focusing panel, a groove at the insertion side of the gate that mates with a ridge on the film holder. Compatible with slip-in sheet film holders as used with spring backs. To add to the fun, up to 1949 all Graphics came with spring backs that Graflex Inc. (and predecessors) called Graphic backs; other makers call them spring backs. Other makers offer versions of the Graflok back, often call it "international back."
To add to the merriment, for a couple of years after 1949 the standard back supplied with Graphics was the Graphic back; the Graflok was initially a higher-priced option. Graflex Inc. supplied Graflok backs to be retrofitted to older Graphics.
About the exceptions. If I recall correctly, Grafmatic magazine film holders will attach to both Graflex and Graflok backs, will slip in under some, not all, Graphic backs. And when Graflex introduced their modern roll holders, ones made to attach Graflex SLRs (roll holders marked Graflex on the back) would also attach to Graflok backs. Graflex Inc roll holders marked Graphic on the back will attach only to Graflok backs. To add to the general hilarity, later roll holders for Graflex SLRs (still marked Graflex on the back) will not attach to Graflok backs.
If you're confused, that's ok. Graflex-speak is confusing.