chapitre "Des lumières aux Républiques"

Fichet lock. Miniature model lock with anti-pick removal and four anti-acid tumblers. The key measures only 2,73 cm, its stem has a diameter of only 2,5 mm and the lock is only 5,78 x 5,82 cm. The informer is triggered by an attempt to pick one of the tumblers a little too high. It then blocks the bolt and the right key can no longer open it. This is how the attempt is signaled. In order to open, the right key must "over-close" the bolt a little more, which re-arms the lock and allows it to open. The tumblers are alternatively made of steel and brass to resist acid attacks destroying the tumblers. So that a simple hook is enough to open. It was assumed that a single acid could not eat away at both steel and brass. Although it is not signed, this lock and its key are the work of Alexandre Fichet in support of his patent n°3883 of March 28, 1829 whose drawings show the key with the same ring and especially the same combination of sizes. It seems that this invention is a shameless copy of Jeremiah Chubb's patent filed eleven years earlier on February 3, 1818 under the name of "detector lock" and which won him the competition launched by the Crown of England for an un-pickable lock.