Lovely little camera! My first one that was (at least in theory) "large format". The roll film backs make it a big winner.
There is no substitute for a film test for the focal plane shutter, although the sound, combined with the accuracy of the slit size can give you an approximation.
Nostalgia too. I had a 2 1/4 x 3 1/4 mini Speed Graphic with both focal plane and lens shutters. Between that and the dark slide there seemed to be an unlimited way to either miss the shot or over-expose the shot. I had roll film backs for rectangular and square formats on 120 or 220 film. Only used sheet film a few times and I still have a few film holders somewhere, if anyone is interested. Stay safe y'all, Bob
Never heard of a focal plane shutter in a camera like this....uses a leaf shutter in the lens and a dark slide for the film back.
Yes, lenses are assembled together with a shutter mechanism, but in those early days there was also a mechanical shutter, a curtain with a slit cut into it, that zips from one side to the other.