No person issuing, selling, or offering to sell any passenger ticket on board any vessel, including the owner or consignee of such vessel or his agents, servants, or employees, shall omit reference to the country of registry of such vessel from any advertisement, circular, circular letter, pamphlet, card, handbill, or other printed paper, or from any other notice, whether written or oral, in regard to such passage, ticket, or instrument of passage or voyage to which it entitles or purports to entitle its owner, purchaser, or holder or the line over which or the vessel for which such passage is sold or offered or as to his agency for such line or vessel. Such reference shall be no less prominently displayed than the balance of the material appearing on the printed paper or other notice.