Quote Originally Posted by David A. Goldfarb View Post
As I recall, the 300mm that I had was flaky in this way. I remember taking the whole system to Ken Hansen where I traded it for credit toward a lighting system, and seeing the guy behind the counter wince when he felt that sandy sensation in the helical.
I had this problem with a Pancolor on my Prakticamat (the fisrt camera sold with TTL metering) nad have similar issues with another Pancolor and a Flektagon & Sonnar all Exacta mount. Meyer lense I bought never seemed to suffer as badly.

My first Pancolor never stopped down consistently to the correct aperture by the early 1960's quality control was poor.