A brass 16" f8 cemented rapid rectilinear lens. The last owner thought it might be Ross or Dalmeyer, but there is no way to know . The aperture adjusts readily - but works opposite to most. Glass is clear, there is some dust to clean out if you wish. Will take great photos , or make a nice display. Circa 1900 is a gueuss. The screw mount diameter measures 67.07 mm approx accross the outside of the threads. 

This is of course quite a big lens. Measures 4" from back to front of the lens hood. Max diameter is 73.5MM acroiss the lens hood. Weight approx 692gm.