Abstract: A machine for marking the location for determining the correct prescription of progressive optical lens including a diffused light source, a platform for supporting the progressive lens intended to be marked in the illumination from the light source, an optical reference element having visible indicia thereon for contact against the progressive lens to locate the symbols on the lens that indicate the position of a reference line thereon, and a marker including adjustable marker elements for contact against the lens in alignment with the reference line, to apply temporary opaque symbols on the progressive lens from which the lens prescription can be determined.