US Patent 9506726 Accessory mounting system for firearms

A firearm having a mounting surface which can include a recess formed on a slide of a pistol. The recess includes mounting posts and a plurality of sights include matching openings and fasteners so that mounting platforms of the plurality of sights can be mounted in the recess in a fixed orientation. The sights of the plurality of sights are movable relative to the platform but the platform is fixed with respect to the recess so that the platform is fixed with respect to the mounting surface. The recess is sized such that optical sights are aligned with original fixed sights.