Various museums (including the British Museum) are lending artefacts from Iran that are in their collection for an exhibition to be held at the National Museum of Iran. As I have mentioned before though, with similar stories, it is sad that countries have to request & negotiate for the temporary loan of what originally belonged to them. In this instance, the only reason for the British Museum’s loan appears to be that it is reciprocating the loan by Iran of many objects for an exhibition there last year.
Persian Journal (Iran) 
Jan 3rd, 2006 – 14:28:14
Most Precious Iranian Artifact Coming Back Home
Jan 3, 2006
A unique collection of Iranian artifacts kept in museums throughout the world will be gathered and displayed at the National Museum of Iran (NMI).
NMI curator Mohammadreza Kargar said that after the recent exhibition “Forgotten Empire: The World of Ancient Persia” opened in Britain, the NMI arranged to display a collection of Iranian treasures kept in the British Museum, the Louvre, the Hermitage, and the Metropolitan Museum of New York.
According to Kargar, the Oxus treasure, including outstanding and characteristic examples of Achaemenid metalwork as well as the Cyrus Cylinder, a clay cylinder of a decree issued by Cyrus the Great after he conquered Babylon that is regarded as the first human rights charter, which are both kept in the British Museum, will be loaned to the National Museum.
He stated that the museum hall allocated for the temporary exhibition is not ready yet, adding that the hall is being established in the northern section of the Islamic Department of the museum.
In 1895, Nasser ad-Din Shah of the Qajar dynasty granted archaeological concessions to the French government. According to the contract, the sum of 10,000 toomans (50,000 francs) was offered to the shah, and it was agreed that half of the findings would belong to the French government. It was at this time when the capitals, the enameled tiles, and other Achaemenid artifacts from Susa were transferred to France to become part of the collection of the Louvre.
The Hermitage and the Metropolitan Museum of New York are also home to ancient carpets, metalwork, inscriptions, and Persian miniature works from Iran.