I have an old brass lens that I know next to nothing about. I've done a couples internet searches but haven't come up with much info.

Curtis Bros and Dublin is engraved on the barrel. It has aperture setting starting at f8 and ending with f44. The sequence is f8, f11, f16, f22, f32 and f44.

It appears to have a lens or group of lens on either end with the aperture in the middle so I'm thinking it is a Rapid Rectilinear but I don't know. The aperture does move but it is very stiff and moves slowly.

Each lens, or lens group on either end is convex to the outside and is concave to the inside. The front part with the hood does unscrew so I could get to the aperture leaves in the middle to clean or oil them.

I see no other markings but the lens barrel is very scratched up. Any varnish coating that may have been on it is long gone.

The diameter of the barrel is 2.5 inches and it is a little over 4.5 inches long including what appears to be the built in hood at the one end. It has no retaining ring but the threads for one are on the end of the barrel.

Is there anyone who may have any information that may help me identify it. I guess I could send it to SK Grimes and have them make me a new retaining ring.