Montblanc MB M16.29

Made at Villeret in small numbers and finished by hand. Its authentication value is that it is unmistakable: the size, the column wheel, the devil's-tail arrow bridge and the quality of the hand finishing have no equivalent in Montblanc's volume production or in any generic movement. Where a watch is presented as a Villeret Minerva, this movement — visible through the display back that these references always carry — settles the question completely. Two numbers are worth checking rather than reading: the beat is 18,000 vph, slow enough that the chronograph seconds hand visibly steps in fifths of a second, and the balance is a large 14.5mm screwed one, both of which are period-faithful choices rather than modern ones. Note also the sibling designation: Montblanc flips the final digit to MB M16.26 for the execution in which the movement is inverted to be viewed from the dial side, so the two numbers denote the same architecture presented two ways.