This is a modern adjustable rear sight. Most likely made for some sort of semi- auto pistol. It is made to fit a 3/8" dovetail .090 deep. Maximum height from barrel to top of sight is 1/2". Has about 3/16" of vertical adjustment. Has about 3/16" of windage adjustment. The adjustable blade in the rear of the sight is reversible and has a round notch in one side and a shallow square notch in the other. I do not know what these were originally made for and I consider them *pull off's* and some of the dovetails show scratching from being installed in a gun. If you do not care about being original, these could be fit to a muzzleloader to have the convenience of an adjustable sight.
