Patent attributes
A firearm having a top surface to which an optical sight is to be attached having a first portion and an adjacent second portion stepped down from the first portion. An adaptor plate is received in the second portion, its shape corresponding to the second portion to properly orient the adaptor plate. The bottom of the second portion and the underside of the adaptor plate having features to receive a spring. An optical sight is attached with at least one fastener to the first portion and directly to the slide of the pistol with a part of the optical sight cantilevered over the second portion and on the adaptor plate. The upper surface of the adaptor plate has a topography that corresponds to a complimentary topography on the underside of that portion of the optical sight.