An interesting prototype of the Summaron 2.8cm, engraved on the front with the special serial number 0000150 and preserved in beautiful, near-mint condition with very good optics. The mount is hand-engraved with the optical formula number B632, the “B” designation being typical for Leitz Wetzlar prototype lenses.This lens represents a development model and shows several differences compared to the later production version of the 2.8cm Summaron. Such prototypes were produced in very small quantities during the optical development process and were typically used for internal testing and evaluation.A rare and fascinating witness to the development of Leica wide-angle lenses. SN: 0000150