Abstract: A sealing system for a container (2) containing a fluid at high pressure, comprising a head (10) moving between a closed position and an open position of the container (2), a piston (12) for the pressurisation of the container (2) mounted to slide within the head (10) and sealing means adapted to prevent fluid from emerging from the pressurised container (2). These sealing means comprise an auxiliary cover (22) adapted to be interposed between the head (10) and the container (2), provided with an opening (24) in which the piston (12) may slide and a coinable gasket (28) associated with the opening (24) adapted after its coining to exert a sliding seal between the piston (12) and the cover (22).