KMZ maintained production of the J-8 in thread mount for the full run, and in my experience- they made the best of the lenses of the USSR. When you find one with markings in English- means they made it for export. The 1975 J-8 was made for export, and is one of the best I've used. KMZ manufactured the Jupiter-3 only until 1956. I have a Valdai J-3 and ZOMZ J-3 that match my 1956 KMZ J-3, but I went through a lot of J-3's to cherry pick them. I'm never had a bad KMZ lens. But- I did have to put a lot of work into my two 1950 KMZ J-3's, figure they were assembly practice for the new fixtures.
And- my favorite lenses are the ones that I CLA'd and/or repaired myself. Using a lens and having the focus spot-on as a result of your hard work is very gratifying.