10 that the assembly of plates 7 comprises is disposed in accordance with a binary code defined by the respective positions of the successive notches when the plates are in rest position fig1 between the plate assembly 7 and the rod 2 there is mounted a feeler 11 constituted by a piece of sectioned sheet metal adapted to pivot about an axis defined by two lateral lugs 11a engaged in slots 12 which extend in two opposite walls of a chassis 31 inside the housing 1 parallel to the direction 6 and offering on a border 1c located on the side opposite the said pivot axis a rectilinear edge 11b applied against the sides 7a with notch 10 of the plates 7 by a low power leaf spring 13 fig2 a to 2d the edge 11b of the feeler 11 is like its pivot axis parallel to the plane of the sides 7a of the plates 7 and perpendicular to the direction 6 of displacement of the rod 2 and of plates 7 the slot 4 for introduction of the key 3 is located opposite the aligned ends 7b of the juxtaposed plates 7 it extends inside the assembly formed by these plates by a series of slots 14 made in the small guiding plates 8 these slots receiving the key 3 introduced into the lock through the inlet slot 4 and more precisely the front edge 3a of the key which comprises a coding represented by cut outs showing hollows 15 and teeth 16 which succeed one another in a determined code the number of binary positions provided on the coded edge 3a is selected so as.