J.H. Dallmeyer Ltd was a long-established British optical firm best known for large-format and cine lenses before extending into 35mm SLR optics in the postwar decades. The 135mm f/4.5 was part of a range of preset telephotos Dallmeyer sold to fit popular continental camera systems of the period.
As a preset design, the aperture is set on a separate ring and the lens stops down just before exposure, a common arrangement on affordable telephotos before automatic diaphragms became standard. It was made for the screw and bayonet fittings used by contemporary German SLRs of the era.
Build quality reflects Dallmeyer's optical heritage, with an all-metal barrel and a modest maximum aperture that keeps a 135mm design compact. Rendering suits simple preset teles of the period: usable contrast stopped down, softer wide-open performance than later automatic-diaphragm 135mm lenses.
Surviving examples are uncommon outside specialist vintage-lens dealers, reflecting smaller production runs than mainstream Japanese and German makers. Check the preset ring clicks smoothly, inspect the aperture blades for oil, and confirm the mount before buying, as more than one fitting was made.