Vessels arriving in the United States from foreign ports may retain on board, without the payment of duty, all coal and other fuel supplies, ships’ stores, sea stores, and the legitimate equipment of such vessels. Any such supplies, ships’ stores, sea stores, or equipment landed and delivered from such vessel shall be considered and treated as imported merchandise: , That bunker coal, bunker oil, ships’ stores, sea stores, or the legitimate equipment of vessels belonging to regular lines plying between foreign ports and the United States, which are delayed in port for any cause, may be transferred under a permit by the appropriate customs officer and under customs supervision from the vessel so delayed to another vessel of the same line and owner, and engaged in the foreign trade, without the payment of duty thereon.Provided