I've posted about this one elsewhere in the forums a couple of years ago...
It's a 1966 Industar-50 3.5/50mm. I bought it and the Zenit SLR it was attached to
very cheaply on eBay, since both were described as "untested", which is usually bad news - but I took a punt on it anyway, given the low auction starting price, and won it for peanuts.
Sure enough, the camera and lens were in a dreadful state... absolutely filthy, lens focusing and diaphragm rings seized, glass infested with fungus. But the body of the lens appeared to be in decent condition and I thought it might be worth saving, so I set to work. I removed the optical elements and carefully cleaned them. Thankfully, the fungus came off fairly easily, and it hadn't etched the glass or damaged the coating. The two halves of the focusing helicoid were seized solid, but gentle heating loosened things up just enough that I could eventually use brute force to unscrew them. Both were cleaned then lubricated with a light marine lithium / zinc-oxide grease. The diaphragm came apart easily, but was badly gummed up with congealed Soviet "ear wax" lubricant that had migrated from the focusing mechanism. That was cleaned off, the blades cleaned thoroughly (some minor wear marks remained), then it was reassembled with just a touch of lubrication on the threaded mechanism, giving a nice dampened feel in use. Lastly, I gave the body parts a very thorough clean with toothbrush and a washing-up liquid plus warm water mix. Under all that dirt was near-mint gloss black paint-work, and lettering that looked yellow was restored to bright white once more.
I've done quite a few Industar-50 and -50-2 lenses in the last few years, and they're usually quick and easy to service. This one wasn't difficult, as such, but took several hours because of its unloved state. I was, and still am, pleased with the result. At 54 years it's older than me and in better condition
- plus, it's the earliest gloss black example I own, and my favourite of the Industar-50 variants
No "before" photos, I'm afraid, and no sample shots from the lens as I've only carried out tests with it... but this is how it now looks: