By the looks of it, that is some type of clipper blade, the type you put a guard on and trim hair to a given length with a different numbered guard. The elongated hole in the end reminds me of where the drive shaft is inserted to drive the mechanism. Just a guess thought, and it's only because I take everything I can apart to see what makes it tick. Probably ground with a bunch of shaped grinding wheels stacked on an arbor.
IF I were going to attempt to duplicate that design with readily available hand tools, I'd probably try a triangular file. To test the theory, you could try laying a tri-file into one fo the grooves and see if it make good contact.
That said, it was probably originally done with some kind of custom grinding/cutting wheel.