Jules LEFEBVRE & Cie, à Paris, seconde moitié du XIXème siècle "Clitograph with frame, projecting ears" in copper-plated cast iron, with a spirit level on the brass tangent (or oscillating) scale. With brass graduated ruler. Signed. 29 x 23.5 cm. Wear, scratches and oxidation. In its wooden box, with Maison label (scratches and bumps; lid slightly off-set). In a February 1873 advertising prospectus, it is explained that "Niveaux-Equerre with protruding ears [...] are intended for use on rulers for unstraightened surfaces, and, therefore, particularly in Building Construction".