Vivitar's scarcer Kiron-built tele-zoom - constant f/3.8 across 70-205mm with macro focusing.
The Vivitar 70-205mm f/3.8 is a manual-focus telephoto zoom from the era when Vivitar acted as a distributor rather than a manufacturer, commissioning designs from Japanese makers and badging them under its own name. This one belongs to the Kino Precision family that also produced the far more common 75-205mm f/3.8, and it sits alongside a separate 70-200mm f/3.8 of different origin. The three are routinely confused in listings.
A 70-205mm zoom with a constant f/3.8 maximum aperture across the range, manual focus, and a macro-focusing capability at the long end that was the selling point of this whole Vivitar tele-zoom line. It was sold in the standard set of vintage SLR mounts of the period. Optical construction, filter thread and weight vary between production runs and are not stated here rather than guessed at.
A 70-205mm range covers portraits through to moderate telephoto reach in one barrel, and the constant f/3.8 means exposure does not shift as you zoom - unusual at this price point when it was current. The macro-focusing setting is what most buyers are actually after; it gets far closer than a conventional tele-zoom of the era and is the reason these keep turning up on mirrorless bodies via adapters.
Prices are low and the supply is thin - this designation is much scarcer than the 75-205mm it is usually mistaken for, so check the front ring carefully before assuming which one you are buying. Look for haze between the internal groups, oil on the aperture blades, and play in the zoom barrel, which is the usual failure on two-touch designs. Front elements on these sit exposed and often carry cleaning marks.