What a beautiful Leica I, David! Amazing! Is it really from 1926? That is surprising, because the vulcanite of this example seems to be cut, so that the lens mounts directly on the metal of the housing, in this case with a spacing ring. This is usually only seen on later Leica I's, around 1930. Could be that I make a wrong interpretation of the photograph. Older Leicas usually have their lenses mount on the vulcanite, not directly on the metal. The lens itself however looks correct for the year 1926.
Erik.