A rugged, releasably attachable or interchangeable optical alignment system well suited for use as with pistol sights includes a sight body carrying a leaf spring locking member adapted to releasably engage a pistol's indentation. The sight body's leaf spring member is inserted into the pistol in a side opening transverse receiving notch with a pinned end of the leaf spring locking member sliding transversely over the pistol indentation's end wall open segment (at the side of the pistol). The user slides the sight base toward the bore's central axis to its fullest transverse extent, whereupon the leaf spring member's first end abuts the indentation's closed end wall. At this moment, the leaf spring locking member's free distal second end springs down and releasably engages and abuts the indentation's end wall, thus releasably locking the sight base to the pistol.