For your consideration is this 1931 production United States Navy Bureau of Navigation Telescopic Alidade Mk.I Mod.I No.66. It is marked U.S. Naval Gun Factory Washington D.C. 1931. Overall condition is good, with all glass intact and most of the finish remaining. The glass is actually very clear. This measures 14.25” long on a 10” base and with an overall height of 4.25”. The green leveling vial is present and intact.