This Mossberg manufactured early variation S102 sporting rear sight is designed for the early model 42B bolt action rimfire rifle which has only one hole for mounting and no rear securing stud hole. This sight has the elevation (wheel) screw marked "Mossberg 2A Pat PDG" or "Mossberg 2A Pat 2132490". The overall condition is good exhibiting a mixture of original blue finish with a brown patina and scattered specks of rust. The mounting screw is included but is the early variation without provision for the knurled windage locking nut. (file photo)