This lens was sold with several brands: Pentax, Takumar, Cosmicar, CPC and probably more. It is from a period when Pentax marketing was run by complete wackos. "Hey, let's take brands built on quality and industry domination in lens coatings, and put them on cheap single-coated lenses built by third-party manufacturers!" Apparently no one ever considered that they were cheapening their own brand.
Here's a link to a review here - photo of the Pentax, review of the Cosmicar:
Pentax Lens Review Database - 70-200mm F4
I have the Takumar-A version, which I've used with my fim camera for about 20 years. It has always had a very low-effort to the focus and zoom control, like manual focus with an AF lens. It's a completely different feel than any other MF lens I've used. It gets very soft at f4 and 200mm - the review says you might not notice at small prints, but I often noticed this at 4x6 on film. Here is one of my early shots on digital at 200mm, f4, 1/180 but welll braced, seems like I focused a bit in front of my target:
At f5.6 or better, or backed off a bit from 200mm, sharpness improves a lot. It has a "macro" close focusing ability at 200mm, which I never used until 3 days ago and is typical of an 80s consumer zoom - the kit lens has better close focus ability. It has a nice 9-bladed aperture. It's pretty big - the Pentax-F 70-210 is 2/3 the length - and uses 58mm filters. It's well built - mine had been dragged everywhere until 2005 and still looks and works like new.
My comments may seem a bit negative. It's one of the few lenses I have that I have used long enough to know its weaknesses that bother me. I still have a sentimental attachment to the lens. I wouldn't pay a lot for one today.