I just inherited a model 18,22 caliber, 4 inch barrel , serial #K396158 that has not been fired in over 30 years. It has no scratches . My brother worked at a gun shop in Virginia and bought it there but sadly passed away 20 years ago . My father held onto it until recently giving it to me. My question is does anyone know about how old it is and maybe how much it might be worth. Thanks so much