The Vivitar Series 1 19-35mm f/3.5-4.5 was an ultra-wide zoom built for Vivitar by Cosina, offered as autofocus continued spreading through SLR systems from the late 1980s and marketed as a Series 1-grade alternative to camera makers' own ultra-wide zooms.
It is an autofocus ultra-wide zoom with a maximum aperture running from f/3.5 at 19mm to f/4.5 at 35mm, sold across the principal autofocus SLR mounts of its era. Weight, filter thread, element count and minimum focus distance are not confirmed from available sources.
The 19mm wide end was unusually short for a mainstream late-1980s zoom, giving strong perspective effects for interiors and architecture, with the barrel distortion and softer corners at the widest setting typical of superwide zoom designs of the period.
It is sought by users wanting an affordable route into extreme wide-angle work on autofocus film bodies. Worth checking: autofocus motor operation on the intended mount, zoom-ring smoothness, and the front element for coating wear given its bulbous, hood-integrated design.