This is a simple matter with some Dallmeyer lenses as the names of the Patent Portraits, Rapid Rectilinears, Triple Achromats and Stigmatic lenses are usually inscribed on the lens barrel. Other Dallmeyer lenses may be less easy to recognise.
The principal lens types are Portrait , Rectilinear, Stereo, Triple Achromat, Wide Angle Landscape and Stigmatic Settings.