Any person requesting a challenged ballot and entitled thereto shall announce his or her name to the official checkers. The registrars of voters or the assistant registrar of voters, as the case may be, shall write, in red ink, before the elector‘s name on the registry list the initials “CB”. The challenged ballot shall be a regular ballot. After the voter has so announced his or her name, the moderator shall deliver to such voter a regular ballot together with a serially-numbered envelope marked “Challenged Ballot”. The challenged voter shall forthwith mark the ballot in the presence of the moderator in such manner that the moderator shall not know how the ballot is marked. The challenged voter shall then fold the ballot in the presence of the moderator so as to conceal the markings and deposit and seal it in the serially-numbered envelope. The challenged voter shall then deliver such envelope to the moderator. The moderator shall retain all such envelopes in an envelope provided by the registrars of voters that shall be sealed immediately following the close of the polls. Such envelope shall be delivered to the head moderator who shall file the envelope with the municipal clerk. The municipal clerk shall retain such envelope until the time when such envelope may be destroyed.