The Optomax 200mm f/3.5 was sold as the 'Auto Optomax' full-aperture-metering telephoto, a faster and later companion to the brand's more common preset 200mm f/4.5. It appeared through the same UK independent-dealer channels that carried the wider Optomax range of Japanese-made budget lenses during the 1970s.
It was produced with automatic diaphragm coupling as standard, chiefly in M42 screw mount, with Pentax K and Exakta-fit examples also recorded in the secondhand market. The extra half-stop over the f/4.5 preset version came with a larger, heavier barrel typical of faster period telephotos.
Owner reviews on Pentax Forums describe it as a solid, sharp performer for the price, giving decent contrast and colour once stopped down slightly, ahead of what its budget positioning might suggest, though it does not match contemporary first-party 200mm lenses in edge performance.
It appears regularly on the used market for modest sums, often under thirty pounds. Buyers should test the auto-diaphragm coupling for a snappy, full-close action, check the focus ring for smoothness, and inspect the rear elements for the haze common in decades-old uncoated or single-coated optics.