Solid Brass Porthole 7" duel Tide and Time clock . The solid brass marine case has been protected twice with a brand new process using Zirconium plating based on Chromium plating. It will never tarnish or discolor. This quality brass clock would be an excellent choice for any marine vessel to add classic nautical flair and functionality. It features a depth of 3.5". The clock works with a quartz movement which requires one AA battery. The movement is accessed through the working, hinged porthole. The clock case features four mounting holes on the base flange and comes with four brass screws. Free brass engraving name plate can be requested.