I have to come to the defense of this lens. I own a nice clean copy and I use it frequently. It's in my 4 or 5 lens kit that I keep with me most of the time - with my K20D.
It's actually a pretty amazing lens if you think about it. It was a pretty unique design and was highly regarded when it came out in the mid 70s, and it has held up well - to the point that it can still hold its own against modern lenses that cost 10 times - or more - what you'll pay for a clean copy today.
I'm a little biased as I tend to prefer manual focus lenses, but I also like good results, and this lens delivers. So much so - for me - that it has caused / allowed me to sell a couple of modern lenses because I didn't use them enough to justify keeping them (one being the Pentax 55-300mm). I simply prefer this lens.
It's very sharp, especially stopped down just 1/2 stop. It also has amazing colors and contrast that rivals some good primes I've used. The macro function isn't bad either.
It is old, heavy, and all manual, but it's also well built and smooth to operate. It's also a verifocal design and not a true zoom - which does take some getting used too - but also contributes to its great optical properties. In the end though, it can produce stunning results for those who will take the time to work with it.
You can check out some user reviews in the lens review database. Most are very positive.
Vivitar Series 1 (Version 1 - Kiron 22xxxx) 70-210mm f/3.5 Lens Reviews - Vivitar Lenses - Pentax Lens Review Database
I am just a hobby photographer. I wasn't really into shooting film, and I never used one of these in their "prime" - so I'm not biased in that respect. I've only used it for the last 8 years or so on my digital pentax bodies. I do have other lenses in this focal range (one is a DA lens) that I use for specific tasks - but if I have the time to set up the shot, and don't have to rush - I'll choose this one over the others.
If I were in the UK and had a Canon that this would work on - I'd definitely be interested. Also, it would probably be fun to mess with - just to see how it works...
Thanks for the offer, and I hope you find a good home for it!