Help with a no-name lens

[B.S.Kumar]

I bought this very nice looking lens in a brass barrel. There are no markings anywhere to indicate the focal length or the maker's name. I hope someone knowledgeable will be able to answer a few questions I have. The focal length appears to be around 180mm, and the image looks quite sharp on the groundglass. It appears to cover 4x5 quite well. Apertures are marked from f/11 to f/64, and the iris moves smoothly. The glass is flawless.

1. As you can see in the 3rd photo, the aperture is physically prevented from opening fully. I know that some lenses have a baffle to prevent people from using the lens below the stated performance. But I've not seen this in older lenses. This lens could easily go to f/8, or maybe even 6.3. Why would it have been done?

2. The lens could probably be mounted in a Copal 1 lensboard. There does appear to be a flange, but it looks like it is painted over, so it is stuck. How can I release the flange without damaging the surface of the barrel? Would paint thinner work?

3. Can anyone identify this lens? There are no swirlies, so it's not a Petzval. Rapid-Rectilinear?

Thanks,
Kumar

[Jac@stafford.net]

Just a WAG, but it looks like a Rapid Aplanat with a jam nut rather than a flange.

A competent repair person could open it up to see if the aperture is mechanically constrained. I'm sure it is.

[Ari]

Kumar, this article by Alex was very helpful in helping me remove a stuck rear element on an old brass lens; maybe it will help remove the stuck flange, after some kind of mild solvent is applied:
http://collodion-art.blogspot.ca/search?q=unscrew+lens

[B.S.Kumar]

Thanks, Jac and Ari. I tried the rubber gloves - didn't work. I'll try what Alex suggests. If it doesn't, the lens will take a short holiday in Osaka next week.

Kumar