Thanks for the additional pictures but they're not much help.
http://camera-wiki.org/wiki/Soho_Reflex shows this type of camera was made from 1905 until 1940.
Knobs were attached in one of two ways usually, the center comes out then a nut or screw holds it to the shaft or a pin goes through the center of the shaft and the small protrusion of the knob. Taper pins were used at first then when roll pins were developed they were used.
I've seen cases where the paint/finish on the knob hid the pin. Careful feeling along the edge close to the body will reveal the pin if it exists. Taper pins are larger on one end, go in and come out one way only. Pins fuse in place and have to soak in penetrating oil for a few hours to a few days before they can be driven out. Use a drive/pin punch and hammer to drive the pin out with a support under the knob to prevent the shaft from bending.
There is a third possibility, the knob screws onto the shaft and is sealed by threadlocker. If threaded it may be left hand thread, anti clockwise in Europe.