Mongo purchased a very well known Vivitar 70-150mm constant f3.8 made by the well known Kiron optical company of Japan in the mid 70's. Mongo knew it was made by Kiron becuase of the serial number on the lens. Not all Vivitars are the same. Vivitar had most of its lenses made by other manufacturers of the time eg, Kiron, Cossina, Tokina, Komine and others. Some of these manufacturers were exceptional - Kiron and Komine were generally considered to be the best of them. The famous Vivitar Series 1 range was largely made by these manufacturers. Mongo owned the famous Vivitar Series 1 105 f2.5 1:1 macro lens which was as good as they say it was.
However, as with many things, each manufacturer got a reputation for producing the best of a particular Vivitar Series 1 lens e.g. whilst Kiron, Tonika and Komine all made various excellent versions of the Series 1 70-210mm macro lens, Komine is though to produce the best of the 3 manufacturers for that particular model of lens (See http://www.robertstech.com/vivitar.htm)
The lens Mongo just bought is not a Series 1 lens but it comes from a manufacturer that makes very good stuff. Mongo paid the outrageous price of $14.00 for it because it had a scratch on the front element. It was otherwise in perfect shape. However, Mongo was more than certain it would not affect the image quality - and , it doesn't in any way at all. It is a very small lens - about the size and weight of a nikkor 105mm f2.5 AI-s.
Based on the results below and the relative pittance these lenses can be purchased for, Mongo is on the look out for the Series 1 version of the 70-210mm made by Komine if he can find one.
This shot was hand held at 150mm - subject about 6-7 metres away. This is a 50% crop. and processed the same way Mongo would process any other image.
This image is also hand held of the neighbour's roof and taken using a Kiron X2 converter which Mongo also has. Subject about 20 metres away and this image is also a 50% crop.