I've never seen one without the antenna terminals either. I sold my Superadio years ago, but have a Superadio III that I use for general listening. It's served me well for years.
I also have an early predecessor to the Superadio series; a 9 transistor GE P780H. It's a great radio and a joy to listen to. It too has antenna terminals on the back. I believe it's from 1964 or '65:
