Nice little lens that to me looks more like a Rangefinder lens than an SLR one.
The only Sonnar 50mm lens for an SLR.
About 1000 were said to be made.
But as with Sonnars, you get than center sharp, soft off center look wide open.
Sharpens up nicely by f4.
If you are looking for sharpness at pixel peeping levels and numerical comparisons as the way to judge the lens, it's not for you.
What you get is rarity, history, uniqueness, the sonnar look.
Certainly sharp enough in most cases wide open, and the soft/sharp rendition of a Sonnar lens.