Brass Dallmeyer London lens. With the mounting flange. Serial number 6708. Per the Dallmeyer Archive we believe this to be a Quick Acting Portrait model 1B Long of 4 3/4" back focus, 2 1/8' barrel dia., pre-patent model 1860s vintage. In modern parlance this should be a 6" Petzval lens. Does not come with any water stops. Has rack and pinion focusing.  Focusing works well. The lens shade is slightly deformed but otherwise in good shape for a lens that's 150 plus years old. Please look at the photos. No haze or fungus on glass.