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Any patent dates previous to 1902 mark it as (almost certainly) a 19th century plane.
Any Bailey plane with a small iron (blade/cutter) depth-adjustment wheel is pre-Sweetheart, as is any with a low knob (there are some Type 11 planes with a high knob, but most have a low knob).
Any Stanley/Bailey plane without frog adjusting screws is pre-1910 [Type 10 or earlier] (except for a relative handful that were made without frog adjusting screws during WW II, but most of those have a Bakelite iron depth-adjusting wheel that mark them as WW II era manufactured planes).
Planes with print on the depth-adjustment wheel are almost all 19th century planes (IIRC).
The plow has very substantial 1/4 inch thick cutters which is a design feature that was probably inherited from wooden plow planes which had thick, tapered blades.
Included with the plane was a boxed set of between 19 to 22 cutters, the exact number depending upon the model year.
Many more special order cutters were available, as well as auxilliary bottoms (similar in concept to the fillister bottom on the 41) for hollows, rounds, and nosing plane applications.
In a wooden plane, the taper on the blade helps to keep the iron tight against the wedge - backwards force on the iron serves to tighten it.
The Stanley 41 uses screw pressure to hold the blade in place, so the only advantage to a thick cutter would be in reducing chatter.