Puzziling, But my guess is the guy that machined it didn't put those grooves in the bottom for no reason, so it must interlock with something I would say. Since it has no markings it tells me its a one off tool made by a machinist or tool maker for a very specific job maybe? My thoughts are a it got dragged down something pretty darn tough, not many small tools with 2 handles unless it was really needed. I would also say a awl, or scribe goes through the holes and then the guide follows what was just cut by the awl or scribe, making the dragging pretty tough, making the need for two handles for a heavy pull but making a nice straight cut. Maybe for scoring ice blocks or something??
Ok I have no idea but its neat!