Having an issue with an eBayer who sold me a Pan-Cinor 20-60 Zoom. The zoom feature was frozen (not mentioned in the ad), and when I took the adjustment ring off, there seems to be parts missing. The set screws on the adjustment ring were going to the body itself, and there's nothing linking to the tab that actuates the zoom. I suspect there was a piece that looked like a shim ring that got removed or left out when someone was messing around with it. I need to document what's missing.
If it's ANY of the Som Berthiot Zoom lenses, that may help. They should all be using a very similar design for the zoom.