OP, thanks for posting the images. They added much clarity.
There's a manual for that camera, miscataloged as for the Veriwide 100, at
http://www.butkus.org/chinon/brooks_veriwide_100/brooks_veriwide_100.htm. It shows the camera with a Mamiya Press roll holder, whose gate is ~ 56 mm x 82 mm.
I don't agree completely with Shutterfinger's comments in post #6 above. I agree with his comment that his black arrow 1 points at the lens cone's retaining ring. I don't agree that his white arrow 2 points at the shutter's retaining ring.
I b'lieve that the shutter's retaining ring is hidden behind the lens' rear cell. To find out, unscrew the rear cell. There should be a slotted retaining ring.
If I had the thing in hand and my guess (educated, but still a guess) is right, I'd use a spanner to remove the lens cone's retaining ring, would then remove the cone from the body. After that, unscrew the lens' rear cell, remove the shutter's retaining ring and remove the shutter and front cell from the cone.
Shutterfinger's comment that the shutter is canted on the cone points to a mounting issue. Many of these shutters were delivered with a tiny screw protruding from the back. This screw was intended to fit a slot or hold on the lens board. When mounted with the screw in the slot/hold, the screw will prevent the lens from rotating on the board. When mounted with the screw anywhere else, the shutter will be canted on the board and may well turn freely. The only way to check is to disassemble as I suggested. If this is the problem, reassemble with the screw in the right place.