Abstract: There is provided a tin lid for flat cans rounded oblong, in Hansa format, which includes in its lid image section, a tear-open portion defined by a self-contained notch line capable of being broken up at one end of the lid by means of a pull-open ring attached to this end. At the other end, said notch line includes a straight-lined notch line section which extends in chordal-type fashion with respect to the core wall shaped like an arc of a circle and which is arranged perpendicular and symmetrically to the longitudinal lid center line and which is connected with the other portions of the notch line through a polygonal or chordal-type connecting notch line. The distance between the chordal-type notch line section and the core wall, measured along the longitudinal center line of the lid, preferably ranges between 6 and 10 mm.