I will call it a 8 Gauge shotshell but in fact this case was designed to be loaded with a bullet and to be shot in a rifled bore gun.
It looks like a regular case but it has a squarred rim and a special more powerfull primer (not a shotshell primer)
This is a product of gevelot before 1885.
We think it is an order from Galand for an elephant hunter
The following pictures show the differences of the rim and of the primer in comparaison with a normal 8 gauge shotshell