Minolta's mid-60s ultra-wide — the 21mm f/4 W Rokkor-QH retrofocus prime for SR/MD bodies.
The Minolta W Rokkor-QH 21mm f/4 is a wide-angle manual-focus lens for Minolta reflex cameras, introduced in the mid-1960s. The W prefix marks it as a wide-angle Rokkor, and it occupied the ultra-wide part of Minolta's range for the SR/MD system in that era. It was a retrofocus design intended to clear the reflex mirror while still delivering a very wide field of view.
This is a manual-focus wide-angle lens with a 21mm focal length and a maximum aperture of f/4. The QH code in Minolta's system describes the internal element and group layout. Only the focal length and aperture are stated as verified here; other construction details for this specific model are not confirmed and are therefore omitted rather than guessed.
At 21mm the lens gives a sweeping angle of view well suited to landscapes, interiors and architecture, where its wide coverage lets a photographer emphasise foreground and take in large scenes. A maximum aperture of f/4 is modest by later standards but adequate for the daylight and tripod work this focal length is usually put to.
On the used market this is a relatively uncommon early wide Rokkor sought by Minolta system users and collectors. Given its age, check for haze, fungus and element separation, ensure the aperture blades are dry and snappy, and verify the focus ring moves evenly. Inspect the coating for cleaning marks, and confirm the filter ring and mount are undamaged before buying.