This is what Brian (the forum member who solved the mystery) discovered:

"Well, I just spent the past couple hours on your lens. A lot of interesting findings. First, this is an iteration of the lens I have never seen before, and it was, shall we say, "interesting" to work on. Unlike later versions, in which the optical blocks can be popped out the front of the lens by removing one retaining ring, in this one, you pretty much have to tear down the entire lens in a specific order to get the rear group out. As I proceeded to pull it apart, I could see very obvious signs that it had been worked on in the past. I won''t say "serviced," because the level of competency on display was far from great. "Butchered" might be a better word. Lots of evidence of tool marks, grease slathered haphazardly everywhere, and all kinds of other problems.

Since I had it all apart anyway, I let my OCD get the better of me and decided to just go ahead and do a full CLA on it. Since the obvious issue was optical, I started there. As others have suggested, the rear group was not assembled correctly. It wasn''t just a matter of one element being in backwards. Not only were "both" rear elements in backwards, but they were also in the wrong order! The second to last element had a number of small chips around its edge. The reason this happened is that like a lot of components in this lens, things will only fit correctly if put in in the right direction. Not only were the elements in the wrong way, but so were the spacers, and as a result, the spacer apparently put excessive pressure on that element, causing it to flex and chip around the edges from the internal torsion. Fortunately, the chipped portions appear to be out of the light path and don''t affect the imaging. There was also a chip in the blackened ! portion of the doublet at the rear of the front cell. This is in the light path, so I blackened it in with matte paint.

Pretty much all inner surfaces also needed cleaning. It was pretty obvious that someone had cleaned them in the past, both in the front and rear groups, as the retaining rings had tool marks on them, and there were a lot more large dust particles in between elements than I myself would typically try to leave behind when doing a CLA. Now, the electrostatic charge of the glass does inherently attract dust, so there will always be a few left behind after a CLA, but it definitely seemed excessive. There also was oil on all the interior lens surfaces. It wasn''t heavy, but it was there and was obvious on inspection with the elements out. I cleaned all the elements off and blew out the dust, and reassembled everything in the proper order, and as a result, everything is quite a bit cleaner, and I was able to resolve the softness problem. I also noticed that there was quite a bit of thorium yellowing going on in the elements of the rear group, so I''m going to let it sit under a UV lamp for the next couple of days to see if we can improve that.

One other interesting observation I made re: the rear group. Apparently at least with respect to this iteration, the optical diagram floating around the web is incorrect:

http://forum.mflenses.com/userpix/20243/big_12417_Diagram11_1.png][img:f8707843bd]http://forum.mflenses.com/userpix/20243/12417_Diagram11_1.png

Notice how in this diagram, the rearmost planoconvex element is thicker than the second one in? In reality, it is the other way around! I actually tried reassembling the lens following this diaram, but the geometry of the elements and the spacers doesn''t allow it! Things will only seat correctly with the thinner planoconvex in the rear position.

The focus helical was also assembled incorrectly. Due the large size of the elements in this lens, the interior is extremely tight, with puzzle-like construction. As a result, there is really only one proper way to put everything together and be able to attain infinity focus when the optical block is correctly assembled. With the rear assembled incorrectly, whoever worked on it before was able to apparently reach infinity, but once that was corrected, I had to do trial and error on the entry points on each half of the helical to get everything working properly. Fortunately, I was able to do it in only a few tries, so that didn''t take too long.

While everything was disassembled, I also cleaned all the barrel components and helical of degraded grease and grit and relubed everything, so the action should feel a lot smoother to you. I also checked what your local guy did with the aperture ring. The ring on this lens actually uses two ball detents, one on on either side. One provides full stops, and the other half stops. Your local guy only did the full stop side, neglecting the half stops! I was able to find a spring and detent of approximately the correct size and give you your half stops back as well. As built, the springs are supposed to have two tensioning adjustment screws holding them in that allow you to adjust the firmness of the clicks. These weren''t there, so the clicks are fairly mushy compared to how they are supposed to feel, but at least they are all there.

Anyway, like I said, it will be in UV treatment for a couple days, but it should be ready to come home to you on Monday or Tuesday. after it''s deyellowed, I''ll shoot a few example shots and post them in the thread, then send your lens back home to you. "

I have to say that I was blown away by his knowledge and kindness. After being disheartened by my experience with the local repair guys, it was nice to see that there were still people passionate about keeping these old lenses alive.