A measurement mark (3) for determining the relative positional accuracy of a progressive projection onto a wafer (5), the projection being performed with two masks (3, 4), comprising two structure elements (10, 20) formed on a respective one of the masks (1, 2). The structure elements (10, 20) overlap with regard to their position on the masks so that, during the projection of the second structure element (20), an electrically conductive structure (30) formed on the basis of the first structure element on the wafer (5) is overformed by removal of a portion (31). In an electrical line width measurement, the reduced width (CD, CD30a) of the structure (30) is measured and compared either with the original width (62) or with that width (CD30b) of a further partial element (30b) produced by the overforming.