This is a square toothed wheel ratchet with two pawls: one to advance the wheel, and the other to check its reversal. The advancing pawl is moved by a crank-operated four-bar linkage. This model looks similar to model N-12, but operates on a different principle. This mechanism advances the wheel one tooth-pitch for every revolution of the crank. Thus, this is a counting device.

Francis Moon 2004-07-00