Manufactured between 1986 and 1988. This is an excellent example of a U.S. Customs Service Model 686 "CS-1" revolver. These revolvers are set apart from the normal 686 by their special matte finish and "CS-1" marking on the inside of the frame. The frame on this revolver is also marked with an "M" indicating this revolver was shipped back to the factory to have several parts swapped out as part of a recall. This example features the 4 inch barrel with pinned serrated blade front and adjustable rear sights which according to the included copy of a Smith & Wesson factory letter for a different U.S. Customs S&W Model 686 revolver, only saw 5419 units produced. Many of these revolvers were sold through commercial means once Customs retired them. The CS-1 Model 686 revolvers were built to the exacting specification of the U.S. Customs armorers in Glynco, Georgia to create a supremely accurate and dependable service revolver which would stand up to the wear and tear of Customs duty. The specification of these desirable revolvers was altered slightly when Smith & Wesson told Customs that the frame to forcing cone gap was too narrow and the revolver would not function properly. The Model 686 revolver served U.S. Customs for only a short period of time being phased out during 1988-89 in favor of more modern semi-automatic pistols, causing only a small number of revolvers to be manufactured.