Leica Summar 50/2 Ltm “Tropen”Serial. 410xxxTop Collectibles. Leitz Wetzlar rare original TROPEN Summar 1:2/5 cm lens. In between the 400.000 serial number range of the Leica lenses, very few series of Summar lenses indicate “Tropen” in the factory records. It is meant that lenses are especially suitable for tropical environments. There are two key-features of the tropical Summar lenses, what concerns their technical standards: First of all, the lenses contain a compound front-element, balsamized of two elements. So in fact, the tropical Summar lenses are of a seven-element design instead of the regular six-element. Second, the tropical Summar lenses have a ball and groove design in the collapsible barrel, similar to the later Summitar lenses. Tropical Summar lenses are extremely rare.