An essential tool for extending exposure times to capture moving water, clouds, etc. and to modify depth of field.  Excellent condition, used sparingly, made in Germany.  Similar models sell new for $90.  Includes original hard plastic padded case and box.

From the manufacturer, B+W:

The B+W 72mm SC 106 ND 1.8 Filter is a neutral density filter with a 64x filter factor that provides a 6-stop exposure reduction. Its 1.8 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than normally required. By increasing your aperture or slowing your exposure time, you can control depth of field and convey movement more easily. Neutral density filters do not affect the coloration of the image and are ideal for pairing with other filters.

To prevent internal ghosting and reflections, each glass surface includes one layer of anti-reflection coating. B+W filters are constructed from SCHOTT glass for increased optical clarity. This filter features a brass filter ring for durability as well as to prevent jamming.