The provisions of sections 192a to 192c of this title shall apply to all existing contracts for the purchase of Government royalty oil entered into after July 13, 1946, and prior to September 1, 1949, irrespective of whether a determination of preference status was made in connection with the award of such contracts, but shall not apply to any such contract which subsequent to its award has been transferred, through the acquisition of stock interests or other transactions, to the ownership or control of a refinery ineligible for a preference under section 192 of this title, and the regulations in force thereunder at the time of such transfer.