Developed by W.W. Greener and based on the 450 3¼ case necked down, but this case has a double shoulder. On the second specimen you will see the flutes on the neck and the idea of this  double shoulder was to provide space for multiple bullets. It also comes with single bullet versions. This multi-ball principle was used on other cases as well, as can be seen HERE.

      Multi Ball version

                                              Single bullet version