Mo. Rev. Stat. § 115.431: Identification certificates to be initialed by judges and preserved as poll lists.

Upon satisfactory identification of the voter, two judges of different political parties shall place their initials on the line where the voter signed the precinct register or, if electronic pollbooks are used, two judges of different political parties shall make the appropriate mark on the pollbook. The computerized or paper precinct register shall then constitute the poll list.