Amazingly complex dual adjustment scarificator. The adjustment mechanism raises and lowers the carriage that contains the blades.  Unlike the more common form the advance of the blades from the housing is not based on the rotation of an semicircular blade but the advance of the entire carriage over an elevate support bar.  The mechanism is cocked with a turn-key system.  All in all a very complex little item.  It is marked A. Mack