(a) Upon receipt by a board of elections; within the time prescribed by section 665 of this title of the mailing envelope containing the affidavit envelope and the absentee ballot envelope, after it has been stamped or endorsed in a manner provided by subsection (c) of such section, shall be opened by the board or a part thereof or by the clerk in the presence of a board member, for the purpose of examining the envelope on which is contained the affidavit prescribed by paragraph 3 of section 663 of this title. The affidavit appearing on such envelope, if properly executed, shall be prima facie evidence of the voter's qualification to become a voter. The mailing envelope and the affidavit envelope in which the ballot envelope is sealed shall be attached and placed in a locked file until the time for counting ballots as provided in section 667 of this title. The mailing and affidavit envelope shall be destroyed at the time provided for destruction of the absentee ballots.
(b) All such envelopes received by the boards of elections after the time specified in subsection (a) of section 665 hereof shall be mailed or delivered to the Supervisor of Elections and retained by him, unopened, until, as permitted by law, the ballots cast at the election are destroyed, at which time the envelopes shall likewise be destroyed, unopened and unexamined.