Nice example of unique example of hybrid bayonet – a child of socket and sword parents. Popular names comes from Charles Louis César Duport, markiz de Pontcharra, who was an inventor in French guns industry in thirties of XIXth century. There were a few variants, with locking ring or half ring spring. One with much wider diameter, for rampart gun.
On last picture it is with Belgian bayonet, inspired by Poncharra 1837.