[lars_bergquist]

That is an early edition of the 'secret' V. II Summilux—the optical design that persisted until 2004, with changes in the mount, and of course with improved coating. I have used a late version of that lens, and it was not only less susceptible to flare than the contemporaneous Summicron, it was better in that respect than the current Summicron! It was very Summicron-like at 5.6 and had its own inimitable but pleasant fingerprint at larger apertures. Buy it.

The old man from the Age of the M2