The fact that the sum of "opposite" numbers in a uniform sequence of numbers always is the same has become famous in a legend about the young Carl Friedrich Gauss who used this property to very quickly calöculate the total sum of the elements in such a se...
(Note that if the six sums give the same number, then clearly this number needs to be 13) Answer for the nonmathematicians: 6! \times 2^6=46,080. We should perhaps suggest Franck Muller to do this limited edition of 46,080 (unique) pieces