I added this interesting lens ( built, according to serial no., in 1935) to my collection of screw-mount equipment, ( to date, IIIc and IIIf bodies, and 35/2.8; 50/2.8; 90/4; 135/4.5 lenses and a plethora of accessories and filters), and agree that the lens from f/12.5 thru 18 to 25, does vignette. However, at f/9 the lens is excellent, producing virtually no barrel distortion. I cannot adequately comment on CA, because I shoot it in B+W only, but results appear reasonably sharp, considering the age of the glass. The lens came with its original bakelite case, and is fairly clean, but I admit it could do with a CLA treatment. This lens “lives on ” my Leica IIIc (body built 1942). At f/6.3 the lens delivers good bokeh.