Sigma's early full-frame ultra-wide — same as IDs 711/955, possible pre-DG version.
The Sigma 17-35mm f/2.8-4 EX Aspherical appears to be the same lens family as IDs 711 and 955 — the pre-DG version lacking digital-optimised coatings. It covers 17-35mm on full-frame with variable aperture and EX build.
Same basic specification — 17-35mm at f/2.8-4 with aspherical elements. The EX (without DG) indicates it predates digital sensor optimisation. HSM on some versions. Adequate optics for the era at budget pricing.
Available for Canon EF, Nikon F, and other mounts. 82mm filter thread. EX build quality. Full-frame coverage. Variable f/2.8-4 aperture. This pre-DG version may lack coatings optimised for digital sensors.
Check against IDs 711 and 955 for duplicate. The DG version added digital-optimised coatings. Modern alternatives vastly superior. Very cheap used. Only for absolute budget ultra-wide needs.