The lens is a Cooke Amotal Anastigmat 2 inch F2.0 ELC. Made by Taylor, Taylor & Hobson, England. This is an up grade to better quality optics as better glass became available. Even today a Cinematographer will buy the newest lenses as they become available. The lens board has two sliding plates that allow the lens to be repositioned in front of the aperture. I'm not really sure why you would want this. Often there is some fascinating, unresolved mystery about these old beauties.