I believe my 500mm f:5.5 Schneider-Göttingen Aerotar may well be even heavier. After all, you weren't supposed to mount the lens on a camera, but rather mount an airplane on the lens!
It seems to be a rather extreme Heliar derivative - 2+3+3 elements - and is one massive chunk of glass.
My 360 Caltar-IIN seems reasonable now. Well, no, not really.
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