probator

noun2

1. •
   An examiner; an approver.

   • Warranted Officers, that are reckoned ancient experienced Men of the same Employments, some nominated, and appointed for Probators, as well as all from the Captains and Commissioners — 1691
2. •
   (UK, no longer used) One who, when indicted for crime, confessed it and accused his accomplices in order to obtain pardon.