The Tokina RMC 28-85mm f/4 was a constant-aperture manual focus standard zoom from Tokina's RMC line, produced from the late 1970s into the 1980s, offering wide-angle to short-telephoto coverage in a single lens for 35mm SLR users.
It uses a two-touch or one-touch zoom-and-focus barrel with a manual click-stop aperture ring, and a constant f/4 maximum aperture throughout the range, simplifying exposure compared with the variable-aperture zooms common at this price point. RMC multi-coating is applied to reduce flare.
The constant f/4 aperture gives consistent brightness through the viewfinder and predictable exposure when zooming, with performance that is even across the frame at moderate apertures and softens only slightly at the wide end wide open.
These appear regularly in M42, Pentax K, Canon FD, Nikon F, Minolta MD, Olympus OM and Konica AR mounts, and remain inexpensive. Check the zoom ring for smooth, consistent travel and confirm the aperture ring clicks are crisp at every stop.