A nice little Gem type petzval probably originally for 4 quarter plates on a single plate. It is 6" focus and will cover 4X5 Interesting construction, unlike the Darlot's I've had before, this one has the front and back glass permanently 'rolled' into the metal barrel like was usual for most all of the later Aplanat type constructions. I don't know who made it. The backwards number 4 is exactly how it is on there. No other markings present. It has a stop soldered inside which if you choose to remove it, the lens would become slightly faster, like 6" f3.8. Last picture showing that it has 2 little spots where the balsam cement is bubbled. These don't affect anything, and are more or less common with lenses this age. We just use 'em anyways. I wouldn't suggest an attempt at repair. It's really of no effect. $195 + shipping.