Here are a Reel Talk link (2014) and a Classic Fly Rod Forum (2009) link with photos from the 1978 catalog with one guy saying he was gifted one in 1958, that discuss the Orvis spinning reel:
My best estimate would be somewhere between 1953 and 1962. There are thoughts that the handle knob changed to the flatter paddle style in '63. The "A" came out in late 1966. If there's an Orvis box aficionado out there they may be able pin it down a little closer based on the box.
Love those Open Face Spinning Reels!(Especially ABU & ABU/Zebco)