Summitar* 2/5cm prototype

very rare prototype of the later Summicron with thorium-oxide element, in correct focusing mount with diaphragm to 22; a small series of these lenses were produced for testing in 1950, three years before the Summicron came on the market, the lens is in excellent original condition (caps), exactly this lens is illustrated in Hasbroeck's 'Leica, A History illustrating..' on page 192