The Vivitar 35-70mm f/3.5 lens is a pretty solid piece of glass. It weighs in at approximately 16oz. It is composed of 8 elements in 8 groups and according to the serial number it is made by Komine for Vivitar. It has a constant aperature of f/3.5 with a minimum aperature of f/32. It is a push-pull design with constant focus and is multi coated. It takes a 58mm filter. It has a minimum focusing distance of 2.5ft for a maximum reproduction size of 1:10@70mm. It has a maximum diameter of 2.7″ and a minimum length of 3″.
I haven’t had a chance to test the lens out, but it appears to be optically pretty good (no real idea till I test it). The issue with the copy that I acquired is that it has a sticky aperature that doesn’t want to open all the way back up easily. When on the camera and you stop it down the aperature will only open back up to about f/4 without rotating the aperature ring back to fully open. I am unsure if I will attempt to repair the lens or return it (it is not in the condition that was described). If I do return it I’ll try to do some sample shots really quick first to test out the optics.
I acquired the lens for $20.