A mailpiece scanner device in a module of a franking system, said mailpiece scanner device comprising: a contact image sensor or “CIS” disposed in a direction perpendicular to the conveying direction in which the mailpieces are conveyed through the module; and a support to which said sensor is fastened and which is mounted firstly to move vertically under the action of at least one drive lever and secondly to pivot about a longitudinal hinge pin; the device further comprising guide means secured to a stationary portion of the module for the purpose of limiting firstly the vertical movement of the image sensor support and secondly pivoting of said support about the longitudinal hinge pin.