A claim for an exemption from duty on the ground that the CBI applies shall be allowed by the port director only if he is satisfied that the requirements set forth in this section and Sec. 10.193 through Sec. 10.198b have been met. Duty-free treatment may be claimed at the time of filing the entry summary by placing the symbol ``E'' as a prefix to the HTSUS subheading number for each article for which such treatment is claimed on that document. [T.D. 84-237, 49 FR 47993, Dec. 7, 1984, as amended by T.D. 89-1, 53 FR 51252, Dec. 21, 1988; T.D. 94-47, 59 FR 25570, May 17, 1994; T.D. 00-68, 65 FR 59658, Oct. 5, 2000]