Here's a plane that others have shown before, but i had it out and apart to take pix, so thought I'd add a few extra pix, and do a quick typing to determine age.
This is a #113 circular plane, Type 4 or 5, approx 1910 based on features. It came with a Q trademark on the iron, and markings on the adjuster gears, and minimal on the knob. Shown below at flat cut, max ID cut, and max OD cut.
I took it apart as someone was having trouble with their frog not lining up correctly to the mouth opening. As you can see from the back of the frog, it has a machined surface which mates to the edge of the mouth. The mouth doesn't seem terribly machined to mate. The step between the machined and unmachined faces is only 0.014" so not much space to work. The other owner was given advice to file things down to fit, which is terrifying. As you can see, the frog being behind the step could be fixed with a shim. IF forward, you may want to thin down the machined surface on the back of the frog.
We speculated that each plane may have been custom fit, and someone played Frankenplane with his, or filed things to make them work "better", but still waiting for a final input from him.
Hope this helps someone. Sometime I will get pic of the other circular plane hiding in the garage. Now to clean up all the sawdust before the meeting ends.