Hmmm ! This thread has sparked my interest as I have several Dallmeyer Patent Portrait lenses (waterhouse stop versions) from a 3B to a 6D from the 1860's as well and three earlier Lerebours et Sectretan petzval lenses (no aperture adjustment less a brass cap that fit's over the front element with a smaller hole in it on one version ) from the approx 1840's and 1850's. Coverage of the Lerebours ( again I have three--2 small and one rather large) is yet unknown but I estimate about 8 inches in FL for the smaller ones. The large Lerebours et Secretan will hopefully have enough coverage for 8x10 but is yet unknown and has a FL of about 290 mm from the rear cell and the lens is about 9 inches in physical length. It is a real beauty!!