All articles which shall be imported from foreign countries for the sole purpose of exhibition or display at a permanent exhibition or exhibitions and/or at a temporary exhibition or exhibitions of the arts, sciences, and industries, and products of the soil, mine, and sea, to be held at any time and from time to time by Rockefeller Center (Incorporated), a corporation organized under the laws of the State of New York, and/or by its tenants or licensees in a building or buildings to be owned by Rockefeller Center (Incorporated), and to be a part of and to be known as Rockefeller Center and to be located between Fifth and Sixth Avenues and Forty-eighth and Fifty-first Streets, in the Borough of Manhattan, city and State of New York, upon which articles there shall be a tariff or customs duty, shall be admitted free of such tariff, customs duty, fees, or charges under such regulations as the Secretary of the Treasury shall prescribe; but it shall be lawful, at any time during or at the close of any exhibition held pursuant to this section, to sell for delivery at the close thereof any goods or property imported for and actually displayed at such exhibition, subject to such regulations for the security of the revenue and for the collection of import duties as the Secretary of the Treasury shall prescribe: Provided, That all such articles, when sold or withdrawn for consumption or use in the United States, shall be subject to the duty, if any, imposed upon such articles by the revenue laws in force at the date of their withdrawal and to the requirements of the tariff laws in effect at such date: And provided further, That Rockefeller Center (Incorporated) shall be deemed, for customs purposes only, to be the sole consignee of all merchandise imported under the provisions of this section, and that all necessary governmental expenses incurred as a result of exhibitions authorized under this section, including salaries of customs officials in charge of imported articles, shall be paid to the Treasury of the United States by Rockefeller Center (Incorporated) under regulations to be prescribed by the Secretary of the Treasury: And provided further, That all such articles shall, at the expiration of two years, be subject to the impost duty then in force, unless the same shall have been sold or exported from this country prior to that period of time: And provided further, That nothing in this section contained shall be construed as an invitation, express or implied, from the Government of the United States to any foreign government, state, municipality, corporation, partnership, or individual to import any articles for the purpose of exhibition at the said exhibitions.