LONDON STEREOSCOPIC BLACK BAND NO. 88031 BRASS LENS

Inside diameter at the rear is 38mm, outside is 41mm. I'm not sure looks like a lens part is missing.
Comes into focus at infinity at 320mm distance to ground glass. I checked it on a 5x7 and image circle covers that. Not sure it would cover 8x10 without vignetting.

The lens is in fairly good condition. Lens has no aperture. The barrel shows moderate signs of prior use. It shows some scuff marks and scratches on the barrel, and some small dings and indentations at the hood. The elements are in very good condition. Shows no cleaning mark, no haze, no fungus, no separation, no scratches, no scuffs. No dust particles in between the elements. Comes with Ø 63mm lens flange. Front Ø 27mm and height approx. 29mm. Lens comes without caps.