The lengths of the links comply with the conditions: A͞D=C͞B and A͞C=D͞B. Thus the basic mechanism of the balance is parallel-crank linkage ADBC. The system of additional levers 2 and 3 deflect hand 1 through the corresponding angle. Weight a counterbalances the weight of pan b and of the links of the mechanism.
$786$LW,B$