It's a brass infill plane, along the lines of a Norris.
They give you the full-sized patterns online and the main plans are in the magazine (Shopnotes, No. 79, January/February 2005). Their website has plans for a block plane in a similar style with enough information for a somewhat experienced woodworker who's not afraid to machine metal to make the full-sized one without the main plans.
We each started with three pieces of Alloy 220 brass, 3/16″ thick, 3″; wide and 12″ long. After making a jig to cut ¾″ finger joints, we formed the joints on both sides and the sole and cut the profiles for each side (cheeks). Total time spent so far was eight hours for jig, joints and profiles for both planes, moving at a leisurely pace.
We each spent about an hour or so separately cleaning up the profiles and the joints.
Another evening (two hours) was spent with a compound mitre saw cutting the throat on each plane (four cuts total, 70° and 45°). Setup time was the longest part. A single bad cut would set us back days at this point.
A Saturday morning (three hours) saw us with soldered bodies (see pictures below). It was nice to get to this point as now we had a three-dimensional project.
Later on, I spent an hour or so with a flat bastard double-cut file cleaning up the fingers (1/8″ proud) and the solder. The instructions suggested using an old chisel but I actually dug into the brass with mine. Not sure if I'll fill it with solder or J-B Weld, but I've got to do something.
I also found that my sides/cheeks bowed inward a bit. I'm not sure this matters and I don't know that I'll fix it. A couple joints need a little bit more solder but I'm stumped there, too.
This is project 200502.