Sigma's 35-80mm f/4-5.6 was a compact, entry-level standard zoom sold during the transition from manual to autofocus SLRs, pitched at buyers wanting a lighter and shorter alternative to full-range 28-80mm or 35-70mm zooms.
The lens spans wide-angle to short telephoto with a modest maximum aperture of f/4 at 35mm falling to f/5.6 at 80mm. It was produced for both manual-focus mounts such as Pentax K, Nikon F, Minolta MD, Olympus OM and Canon FD and, in later runs, autofocus mounts including Canon EF and Nikon F, in a small plastic-and-metal barrel.
Its short length and low weight make it an easy travel companion, though the slow variable aperture limits its use in dim conditions and the outer field of view softens noticeably compared with the centre.
Because it was a budget model, surviving examples vary considerably in mechanical condition. Check the zoom action for looseness, confirm the aperture ring or autofocus coupling still engages correctly, and look for internal dust that has migrated between the groups.