Failed attempt - only the gut is left, but still usable on the helicoid. This lens is from either the Hi-Matic S or Yashica Electro 35. It's a 45mm f1.7 lens.
The very well regarded Zuiko 42mm f1.7 Lens vs the garden variety 40mm f1.7, that few other makers use (Canon, Minolta, etc).
I am taking this slowly, and try to take the time to understand how they are put together, so that when I take them apart, I can still adjust the aperture/focus. Many of these that I disassembled, have seized aperture rings. I am not a patient person and sometimes I just wanted to take them out quickly and used excessive force when seemingly there are no way to remove certain parts of the lens. These usually ended up as lenses with no aperture control, and being used on the focus helicoid. I try to preserve as much as possible the built-in focus mechanism, but the side effect is that each one will need its own mount, which will add to the cost. It also means no close focusing capabilities.
Some recent additions.
The reason I like these rangefinder lenses, is because they usually have pretty fast maximum apertures (f1.7, f2, etc) and they have short flange distance, which match up nicely with mirrorless cameras, especially the full frame A7 series. Let's not forget the most important aspect of these gems, that they have very nice, sometimes unusual rendering characteristics not found in your kit lens or even the very expensive, well corrected fast primes. These things are sometimes like drugs; once get hooked, it has to go through its course to recover, and sometimes you don't!
Yashican Color-Yashinon DX 45mm f1.7 on Sony A7. Looks nice, no?
Empty Milkweed Pod - Nikkor-H 48mm f2 from Nikkorex