The design of Hohner Corona ii was changed quite a bit over the years. The Corona II is a double voice (Two Reeds Per Note), the Corona III a triple voice instrument (Three Reeds Per Note).
Here is a list of hohner corona ii and corona iii from the late fifties to the eighties.
Corona II GCF- turning sixties, Corona II GCF, sixties, Corona II GCF, seventies lower row Corona II GCF, eighties, Corona III BbEbAb, seventies, Corona III BbEbAb, eighties
The Hohner Corona ii classic keyboard is made of wood not plastic like the Panther and the Corona II 3500. The buttons are easier to play than the Panther buttons.