I recently acquired a collapsible 50mm Summicron, vintage 1954, which seems in very good condition, as a suitable companion for my M2, which I'm just sending off for a CLA. On the bayonet mount of the lens, inside the U-shaped notch that's used to lock the lens in position on the body is stamped a tiny number 8.
These numbers don't seem to appear on later lenses. Anyone know what they signify?
David