speed graphics i don't believe ever used
the same film holders as graflex slrs ...
the graflex slrs used the grooved / slotted holders
the spring back cameras, speed graphics and
anniversary graphics, and crown graphics all
used "normal" ungrooved/unslotted film holders
you might want to poke around graflex.org, it is a place
that talks about all the graflex / graphic cameras from the very early ones
to the late model ones .. and the people there and archives there are very nice !
i searched there using this " film holders spring back " and got this:
have fun !