You’re looking at a reproduction of a Stanley #113 compass or circular plane from KUNZ of Germany. A compass plane has a rounded sole for planing curved surfaces. Some compass planes have a fixed sole, but others have an adjustable sole like the one above.
You adjust the curvature of the sole to match the shape of the work piece, whether convex or concave (or possibly even flat, though why you’d want to is beyond me). The hand knob changes the shape of the sole via some cool levers and gears, and a dovetail connects the steel sole to the cast iron plane body.
The entire plane measures 10-1/8″ from front to back and uses a 1-3/4″ blade. The whole thing runs about $300.