Abstract: A locking system comprising a fixed portion secured to a box with a slot for inserting an article to be protected, and a movable portion with a latching member for partially sealing the insertion slot in the locked position. The system further comprises means for preventing the movable portion from being moved unless a specific tool is used. The fixed portion has a rear guide extending in a substantially longitudinal direction, and a front projection with an opening having a substantially longitudinal rear section and an angled section extending therefrom up to the upper edge of said front projection.