Very nice vintage Zeiss, Jena Tessar 25cm f4.5 X2 lens. Nr. 451200. Comes with metal hood and leather cap.

Found a website that puts that serial number in 1922. Lens looks older than that in my opinion.

Perhaps the experts can chime in?

The elements are very nice. Although the rear element has some strange spots. They look like they have rainbow colors. Not really sure how to describe them. Hard to photograph too. 

There appears to be some dust or bubbles between the inner two elements. I could not get them apart to give a clean and I didn't want to force them!

The aperture blades are very smooth. The body shows some wear from age. See photos for details.