Solid geometric congruenceTwo very special and "interdependent properties" are found: the dually identical "elements" and the mirror property of the isolines between "upper" and "lower" parts.
The Otto Möckel (2#) book contains isoline drawings of Stradivarius and, Guarnerius del Gesu instruments. These isoline patterns of Möckles are in surprisingly close congruence with the geometric model, except for very slight deviations which can be explained by age-related deformations in the instrument or by less accurate craftmanship, and of course by the used measuring method of the isolines.The isolines measured by Möckel, are in closer agreement with the geometric model than the average values assumed by Sacconi.