Dan Beck wrote:

====snip====

The blade is heavily cambered which you can see in this photo:


https://groups.io/g/oldtools/photo/268441/3308617?p=Created%2C%2C%2C20%2C2%2C0%2
C0


But here’s where I need help - the entire sole of the plane is also heavily
cambered:


https://groups.io/g/oldtools/photo/268441/3308618?p=Created%2C%2C%2C20%2C2%2C0%2
C0


I’ve not seen this before. Is there a reason for this heavily cambered sole?
Perhaps this was meant for boat building or some other specific task? I’m in the
dark but intrigued so if anyone can enlighten me, I would appreciate it.

====end snip====

I agree with Bill Ghio that it is a backing-out plate. Did it come from an area
where wooden boats are made or maintained?

I had to have some planks replaced on my wooden boat a few years back, and the
shipwright doing the work showed me a backing-out plane and explained what it is
used for (fitting the back of the plank to a curved frame).

Peet Leenhouts has experience in this area. Pete, are you listening?

Cheers,
Chuck Taylor
north of Seattle USA