(a) Period of retention. The Administrator may destroy any disclosure statements or orders, together with the files and folders, as useless or obsolete, 4 years after the date of receipt or issuance. A permanent record shall be maintained of any civil or criminal enforcement of this Act by the Administrator.
     (b) Microfilm. Copies on microfilm or in other form which may be retained by the Administrator in his discretion of any records destroyed under authority of this Section shall be accepted for all purposes as equivalent to the original when certified by the Administrator.