In order for a ship to acquire a certificate of nationality, it must have been admitted to one of the registers of shipping. If you have lost your certificate, you can apply for a new one.
Once the registration has been completed, a final certificate of nationality will be issued. The certificate of nationality documents that the ship is registered in the Danish International Register of Shipping (DIS). DIS is a protective register for ships as is the land register for real property. Through registration in DIS, the owner acquires protection of his ownership to the ship.
If you would like to read more about admission to the register, see under the Initial registration/re-registration to the danish ship registers.