A system for measurement of a can seam of a can comprising a an end panel, the end panel comprising the seam, the seam comprising a circumference, a seam top, a seam bottom, a seam chuck wall part and an opposite seam wall essentially opposite the seam chuck wall part, the system comprising: a table comprising a table top; a rocker comprising an inner pin and an outer pin essentially parallel to each other, the rocker configured to allow, when the end panel of the can is facing the table top, slight pressure of the outer pin on the opposite wall forcing the chuck wall part on the inner pin, and/or slight pressure of the inner pin on the chuck wall part forcing the opposite wall on the outer pin, causing rocking movement of the pins, that settles the inner pin flush with the chuck wall part, and/or the outer pin flush with the opposite wall, respectively, such that the inner pin and outer pin are disposed at chuck wall angle; means for rotating the can, allowing the inner pin to settle flush with the chuck wall part, and the outer pin to settle on a peak point on the opposite wall, at measurement points on the circumference of the seam, and measuring means configured to be able to measure a gap between the inner pin and the outer pin at the measurement points.