I have recently been given old(ish) Sigma 55-200mm lens for Canon (not EF mount), I believe that it is f/4-5.6. It is zoomed by pulling the barrel out.
What mount is it? And what specifications does it have in comparison to the current, equivalent lenses?
Below are some photos of the lens:
The lens, contracted : expanded
the front end : the mount
The mount end, with mount cap
The lens is for the Canon FD mount, and probably saw use on some variant of the Canon AE-1 35mm SLR or the consumer-level T series of cameras. (The FD mount was also used on the Canon F1n and T90 professional series of cameras, but then, as now, professional bodies tend to see mostly brand-name professional lenses.)
The FD mount essentially went obsolete when autofocus showed on the scene; the EOS 35mm cameras used the Canon EF mount. Along with the electrically-driven autofocus, the EOS system also used controls on the body to manage the lens aperture, eliminating the aperture ring.
You can use the lens on an EF/EF-S mount camera, but it requires an adapter and cannot focus at infinity without an additional optical element, which will change te effective focal length and reduce the image quality. There are several places on the web where conversion instructions are available if you have access to machine tools (or a machinist), and there are probably people offering conversion services at some charge, but you'd have to decide whether the conversion would be worth the trouble and expense for you, given that a lens with a similar focal length range and variable aperture, designed for the EF mount from the beginning, is not particularly expensive new and ought to be available used as well.
