Faulty M39 Jupiter 11 on Leica IIIc

I found this beauty on a fleamarket in Ostend, Belgium. The price was 60 Euro. Nothing wrong with the Jupiter 11, the Leica IIIc has a slow first curtain and a bit faulty slow speeds, but that's for later,... The strange thing is : this russian lens was made for a the early Zenit's with a M39 fitting before the got the M42 lensfitting. This lens works only at closer distance because the distance between film and lens is different between M39 and M42. So this combination only works for macro. Can you imagine the impossible work to get something macro sharp with this rangefindercombination! Anyway good lens, good camera, good price, happy me!