The serial number for the mechanism can be found in a number of different locations on the top plate, around the perimeter or in the central area of the movement depending on the specific model; but if a movement has a serial number, it is ALWAYS on the mechanism, NEVER on the watch case. Model 10 and Model 11 Seth Thomas movements have no serial numbers. Some Seth Thomas Model 12 and Model 13 movements have no serial number, and some do have a serial number.