Perhaps someone here can shed some light on my favourite lens which I've had since 1976.

It's marked up as a Vivitar Series 1 200mm but f2.8 rather than the f3.0 which seems to be usually mentioned.

It was picked up in Japan in June 1976 and brought back for me by a family friend along with an AE1 body for the princely sum of 180.00 which seemed like a lot of money at the time.