thats massive Stephen !

Bentens is a true variant and his is the 'no rivet' variant. Probably does have rivet and just a drop of brass solder on it behind and polished out then plated. It's also one of the few that has a hint of a hallmark [?] of some kind on it....

I've also seen a no rivet ruined from the ground that the skull just had a thin 'nib' protruding on back of skull. Could be a drop of brass solder in a pre drilled hole [slightly large to allow for escaping gas] and skull just pushed on.. Skulls always had that tell tale upside down heart nose and either smooth band or hand embellished band.....

As mentioned a few years ago they were kind of on the common side. Now rarely seen for sale.....