That appears to be a filister plane. It’s used for cutting rebates across the grain as well as along the grain. The veritcal cutter is to score the fibres ahead of the blade to prevent tearout. From the pictures, it looks like the blade is skewed which will pull the fence against the workpiece and will give a cleaner cut.
Nice find!
Peter in
Biggar SK
"New York is big, but this is Biggar"