This is Pentax' standard standard lens of its era. It works on just about anything Pentax. You'll find many of these stuck on the fronts of the Pentax K1000 and the Pentax ME. The 50mm f/1.4 and f/1.2 were less common, while the 50mm f/2 and 40mm f/2.8 were cheaper alternatives. Like almost all 50mm standard lenses, it is extremely sharp. Even better, it's a very handsome lens. It just looks right. Call me crazy, but remember that photography is a visual art. If you can't appreciate good industrial design, you're toast.