Pursuant to 19 U.S.C. § 1508(c)(3), all records which pertain to the filing of a drawback claim or to the information contained in the records required by 19 U.S.C. § 1313 in connection with the filing of a drawback claim must be retained for 3 years after liquidation of such claims or longer period if required by law (under 19 U.S.C. § 1508, the same records may be subject to a different period for different purposes).