Thread: Large hone

I picked up a hone at a flea market today and it's pretty big at 12 x 4 inches. Brick colored on one side and black on the other but no markings as to manufacturer. The box has a slot for another small stone (?) but that was missing. Seems fine enough grit to possibly use with razors. Is anyone able to shed some light on it and if I might use it for honing razors?