N.J. Stat. § 19:14-26: Preservation of envelopes and ballots returned by postmaster

The county board, commissioner, or superintendent, as the case may be, shall preserve all envelopes and sample ballots which shall have been mailed by the district boards but returned to it or him by the postmasters of the various municipalities of the county, for the space of six months and the same shall be open to public inspection for the space of three months after the primary or the general or other election, as the case may be.