recently I have found this nice Jupiter 9 with KIEV mount. It was built in 1951 so I took a closer look at it. Inside it is Sonnar from a batch of 2000 made in 1946 (according to Thiele on 6.2.1946).
It was hard to move so I tried to open it. It is easy to disassemble relube and reassemle if you have instructions how to do it. I have found them on Kiev Survival Site.
I had no problem with my Jup 9 s/n 5000135, (2)850958 for the Zeiss number. Same original date as yours and really not far. But mine is a LTM, not difficult to disassemble when the main screw is not stuck. For that time, all was OK...
I have had fear before because of the big spring, that I have seen in the disassembly instructions But it's really easy, there is only one focus helix and you only have to mark one position. Now it works really smooth.