This brass alidade has folding sights that are centered on the beveled edge. It belonged to Mount St. Mary's College in Emmitsburg, Md. A label in the box reads: "Lerebours & Secretan, Secretan Successeur, Optician de S. M. l'Empereur, de l'Observatoire & de la Marine. Magasins: 13, Rue Du Pont-Neuf, Ateliers: 9, Rue Mechain, Faubg St. Jacques Paris." The address of the atelier suggests a date of around 1870. The firm was still in business in 1930.