This is the remains of some kind of ancient Ross lens.
Threaded at both ends, but the front of the barrel is empty. At the back is an achromatic meniscus that makes a nice soft image
Focus at infinity seems to be at about 13 1/2" or thereabouts. It covers 8X10 handily although it gets pretty mushy out at the edges. I'll include a couple images in another post.
For a firmer image, think 5X7 and what a lovely portrait distance 13 + inches is for that format.
I don't have any illusions of great value, but I think
$185 is fair.