[jnovek]

My money's on that this lens is a Cooke Triplet http://en.wikipedia.org/wiki/Cooke_triplet which was (and is) a fairly neutral lens design.

There is some astigmatic aberration as well as vignetting visible in the photos provided, but it's possible that this lens was intended for a smaller image circle than 24x36 sensor in the 5DmkII. All lenses will have astigmatic aberration and vignetting at the edge of their image circle (which is normally outside the photographic media the image is being projected onto).

This lens is uncoated and highly susceptible to lens flare. As I understand it, many lenses before the 4-element Zeiss Tessar also tend to have more pronounced flare than later lens formulas. You can really see this in some of the photos.

Overall, it's neat little lens and I would shoot it in a heartbeat. It looks very sharp in the center with gentle fall-off near the edges. The owner could go a long way to get the most out of it by crafting a little lens hood for it -- it really helps with older lenses like this.

[kjuhyghjk]

And this lens is likely to be f5.6 or slower - it's a lot easier to make a 35mm f5.6 design than a modern f1.2 !

[jacobolus]

f/5.0, the link said.