Method for providing a referencing element to an optical lens member. An optical lens member is provided which has a first optical surface, with a surface design associated with a first reference system, and a second optical surface to be manufactured. The first and second optical surfaces are connected by an external periphery surface. The first optical surface of the optical lens member is measured, and the first reference system is determined. The reference system is determined according to the shape and orientation of the first optical surface. A referencing element is added to the optical lens member, with the referencing element identifying the first reference system.