This is one of those questions that I suspect Brian would have had a very good answer for, but I'm hoping other "regulars" can chip in with suggestions.
I have a 5cm f/1.5 CJZ sonnar, SN 267xxxx, which I'm taking apart in order to clean oli off the aperture blades, clean, and also to blacken the outside or the front triplet. The front retaining ring came off quite easily, but the one holding the triplet is not moving even with a significant amount of force. I don't want to mar the slots, so was thinking that a small amount of lubricant (kerosene? napetha? WD40?) applied with a toothpick might reduce the friction required to remove it, but I'm a little leary of using WD40. Any suggestions?
The lens is in very good shape but does have some very fine cleaning marks on both the front and rear elements. Were the coatings on these early "T" sonnars softer than post-war coatings?
Thanks,
dsymes