Wait for better replies, but if I saw it I would suspect that it's a repurposed projection lens, maybe a petzval. No iris or slot for stops, the focusing wheel removed and there are signs of it having been heated, maybe for soldering the lens shade on.
Well it being mounted with flange and brass sleeve on a “1900” period Studio bipost setup suggests it could be pre WHS era Petzval or made in the 1860’s/70’s by the French maker who didn’t fall for the English invention!
The various sections of differing “patina” surface appearance suggest that it was first used on a more primitive camera with the tangential drive intact. Then moved over to this “modern” camera with fine focusing movements and the pinion drive removed and exposing/covering different section of the brass barrel to the atmosphere!
Bookmarks