Our antiques maritime De Wit brass gauge for sale looks like it could have measured some sort of electrical current and/or pressure of some sort on the vessel. The undamaged glass on the top side of the dial measures about 5 1/4 inches wide. The main housing measures about 5 3/4 inches wide. The mounting frame around the front glass measures 7 inches wide and has three mounting holes. The connection point for the source being measured is made of brass. When mounted to the wall, this pressure gauge will extend out from the mounting surface by about 3 1/2 inches.  While the housing is painted black, it is mostly brass under the paint. The surface on the back side of the gauge is not brass – I would say this section is aluminum.