Leica Summikron 5cm/2 'Prototype A'

as a successor of the Summitar 5cm, this lens came with a new optical design and rare earth glass with special capabilities, the later spelled 'Summicron' became world famous; the first 4 prototype lenses were un-numbered but marked with 'A'; 'B'; 'C' and 'D'; hence this lens here is the first prototype lens ever; very nice condition, with some haze behind the front element; formerly part of the Georg Mann collection.