Good morning, Vince;
This is not going to be easy. First, yes, I do have a Canon Pellix-QL also. These probably can be considered to be "a camera ahead of its time." If you look at the rapidly rising popularity of the digital cameras today with such a system in them, the Pellix really did have a novel concept. It just needed some time and a couple more developments to really catch on. And then there is the variant of the concept which does not have a mirror, and instead uses the "live view" method for framing and focusing, if you are not in the AF mode.
A. I do not really know if that specific defect is common, but problems with the Pellix mirrors are fairly common now. They are 50 years old now, after all. 9. Just about any 35mm film camera, except for Leica, can be bought for less than $100 now, so it is hard to say. 28r. Not true. It is possible to have a mirror redone. How much money can you devote to the project? y. If you can see well enough to focus the lens, then I say, yes, go ahead and use it. 04. Probably. They will have some value even to collectors just because they are unusual from that time period. My own cameras are not "hangar queens" that just sit on a shelf. In my area, a CLA for a 35mm camera will run between $120 and $150. My local camera shops are very happy with my efforts to prolong their continued operation. 2u. I have no specific valid information that will enable a definitive response to this one.
And, for you, where did those line identification prefixes come from?
Enjoy;
Ralph
Latte Land, Washington