The Bendix coaster brake arm reads “patent pending”. Bendix had two CB hub patent designs for their “Red Band” products, about 1961 and 1963.
But patents do not stay "pending" forever.
They may have stamped an “RB” or “RB2” on the brake arm. These may give you a ballpark date range, if the hub has 1 red stripe (band) around the middle. If no stripe (band), then pre-61. These middle weight bikes, with 1.75" wide tires,were first introduced in the late 1950's, and that was about the time that metallic candy-coat paint was introduced.