The size of this lens is shockingly small. It's absolutely tiny and weighs almost nothing. Like all OM Zuiko lenses it's a spectacular lens to use. Performance is surprisingly mediocre though but I view this as a compromise for the size. Did I mention that it's small - because it's stupidly small. You can get them pretty easily as it seems they're quite common.
Mount: OM Mount
Focal Length: 135mm
Aperture Range: f/3.5 - f/22
Minimum Focus: 1.5m
Filter Thread: 49mm
Data Source: All Photo Lenses - Lens-DB
Date Acquired: 06/01/19
Serial Number: 1022117
Purchase Price: $50
Going Price: ~$60
Condition: Near perfect
It's an OM Zuiko lens - I don't really think I need to say much more about the mechanics. The focus is silky smooth and the aperture (like all OM Zuiko lenses is at the front of the lens) clicks easily. The lens has an integrated hood which is always handy and the small size eliminates any excuses for not bringing it along. I really can't find any faults with the build of the lens. It's damn near perfect.
Lens performance is where things fall apart a bit. Compared to the stunning performance of lenses like the Canon nFD 135mm f/3.5 or Konica Hexar AR 135mm f/3.5 this lens is a bit underwhelming. The center is tack sharp wide open but the corners aren't sharp until f/8 which is disappointing. Vignetting is well controlled by flare is pretty bad with a distinct blue band being rendered in the torture test. Bokeh is quite smooth though and never renders distinct polygons.
The lens in use is pure joy. The small size makes handling a breeze and negates excuses to not use it. I didn't have any problems landing focus. Overall it's a good lens if not amazing.
Should I get one for photography?
If you're not already invested into Olympus OM glass then you probably shouldn't. There are cheaper lenses that perform better out there. Yes they're larger but the image quality out of something like the Konica Hexar AR 135mm f/3.5 is vastly superior. If you are invested into Olympus OM lenses then this one is worth adding to your set but I wouldn't go out of my way for it.
Should I get one for a collection?
Olympus OM glass have a fairly ardent following making them worthwhile collectors items. Even if you don't intend to shoot with them the fantastic build and unique mechanics make them interesting. Plus they don't cost too much money which is always a nice thing.