Upon receipt of a return envelope containing an armed services or overseas citizen federal election absentee ballot, the clerk of the city or town shall open and retain said envelope and deliver the affidavit envelope to the supervisors of the checklist of the voting place indicated thereon. If the voter is not registered, the appropriate affidavit appearing on said envelope, if properly executed, shall, subject to N.H. Rev. Stat. § 657:23, be prima facie evidence of the voter’s qualifications to become a voter and his or her name shall be added to the checklist at the next session of the supervisors of the checklist. The supervisors of the checklist shall retain a copy of the affidavit envelope and absentee ballot request form in accordance with N.H. Rev. Stat. § 33-A:3-a and return the affidavit envelopes unopened to the city or town clerk who shall see that they agree in number with the mailing envelopes. Said clerk shall attach the application for an armed services or overseas citizen federal election absentee ballot submitted by said voter to the 2 corresponding envelopes and retain them until election day.