This Sigma 600mm f/8.0 Mirror-Telephoto lens is in very nice condition and comes with a Canon FD mount.  It offers a maximum aperture of f/8 and includes insertable - ND 4x, O56, Y52, and R60 filters. The lens is all black and in nice shape with no discernible body scratches. Lens/mirror elements have no mold, fungus, or dust.  Focus is smooth.

Comes with everything shown in photos:

I have been using this lens on a Sony A7R2 with an adapter and usually a tripod. It is VERY crisp at infinity and, with practice, decent images can be captured at all distances. A few photos of backyard birds at 50 feet are included.