Upload & Sell: On
Ok, so I've been looking for a 55/1.2. There are a couple on ebay, but they all look different.
There is one at Igor's which says it's an AI converted lens, and another one at Cameta (more$$) which is a genuine AI, but the focusing ring looks totally different (it looks like the 50/1.2, without the big fluted focusing ring).
Which model/style of 55/1.2 should I be trying to find?
I'd suggest that you visit this section of the photosynthesis database...
You will see a listing for a variety of 55 f/1.2 lenses. The 50 f/1.2 and 58 f/1.2 were only produced as AI and AI-s lenses, but the 55 f/1.2 goes back much further. It was produced as a pre-AI lens in a number of forms, each slightly different in optical design or form factor. For pre-AI lenses, it is possible to convert them so they will work with modern cameras that accept AI and AI-s manual focus lenses. That conversion can be accomplished with an AI conversion kit from Nikon or by cutting town the aperture ring, which is done by a number of folks. It can be done well or poorly. My personal preference is for a lens that has the Nikon AI conversion kit installed.
At the database, you can click on the name of the lens which is a link to a photograph of what that particular lens looks like. You would need to shift from the Serial number database to the Specifications database to learn about the optical design, but with this database you can see photos of ALL the different versions.
Here is a photo of the 55 f/1.2 S-C AI'd. At the bottom of the lens, adjacent to the camera mount you will see small aperture numbers. That is what you'll find on a lens that has the Nikon conversion kit. Without those numbers a lens identified as an AI lens will have the aperture ring cut down.
Here is an S version of the pre-AI lens that was converted with the kit...
55 f/1.2 S AI'd
Here is an S-C version that has NOT been converted. The S-C had multicoating that was not used in earlier lenses, but is used in later versions.
55 f/1.2 S-C NON AI
And here is an S-C version that HAS been converted with the Nikon kit... the gold standard for knurled 55mm lenses.
55 f/1.2 S-C AI-dů the real deal!