I need help i have a s w 6 hole revolver that breaks over.a 38special falls thru the cyl. the only numbers on the bottom of the round bottom diamond grips are 7778. four inch barrel. does anyone know what model or year by this discrpt. is the gun is rusty. if i knew where to look i might be able to use a magnif. glass.on the barrel says smith and wesson springfield mass usa pat pend july 25 65 thanks for any help