I got back the '51 KMZ Jupiter 8 which had been in the shop for most of this year. It seems to function alright but it is still cold so there is some fog on the internal surfaces. I will run it against the Cooke Amotal, '57 KMZ J8 and see how they all fair, when the '51 warms up. My '57 is awfully good so I am interested in seeing how this alleged '51 stacks up. The original design, Zeiss, is good. If I understand correctly the Russians used German parts to make the early J8's and then fabricated their own using kidnapped German techs and later their own techs. A good Jupiter is a good lens. If mine is not dialed in on focus it will be. The J8/M9 combo is a good one as can be seen above.
Looks like it has the "back focus" problem which means the camera shop that had it missed this. There is another shop which has been accurate, fast and reliable in the past and I suppose it still is. I have a few lenses that can be checked.