A candidate for the certificate of qualification as efficient general purpose rating (port operations) shall have—

the 18 months' qualifying service shall consist of at least six months served on deck, at least six months served in the engine-room and the remaining six months served either on deck or in the engine-room, and during that period the candidate shall have held the certificates of qualification as wiper and ordinary seaman (with or without the port operations limitation) or have gained the combined sea service required by regulations 42 and 44;