Abstract: A padlock type marking seal having a receiving body (2) with internal locking teeth (4) to receive the tip (9) of a loop of the seal that is integral with the body, and there being a marking tab (6) also integral with the body (1). In order to improve seal application, to ensure autopenetration into the material to be marked (e.g. meat), the tip is sharpened and there is a stop (11) on the loop, adjacent to and behind the tip so as to allow an applicator device to force the sharpened point to penetrate the material to be marked. The loop of the seal has a reduced thickness region defining a pivot point (8) with respect to the body, and the part (7) of the loop between the first end and the sharpened tip is substantially in the form of the arc of a circle. A reception cavity (3) in the body of the seal has an axis substantially tangential to the arc when the loop is pivoted about the pivot point, until its tip begins to enter said cavity.