A convict who shall pass the entire period of his imprisonment without a violation of the rules and discipline, except such as the Warden or Board of Control shall excuse, shall upon his discharge from prison be restored to the rights and privileges forfeited by his conviction, and shall receive from the Governor a certificate under the great seal of the state as evidence of such restoration, to be issued upon presentation to the Governor of a certificate of such conduct, which shall be furnished to such convict by the Warden.