In cities of the first class the president of the board of education be and is hereby authorized and empowered to adopt and use a rubber stamp signature on city warrants which have to be signed by him: Provided, That a duly attested copy of said stamp signature shall first be filed with the city controller: And provided further, That all of said warrants shall be countersigned, as heretofore, by the secretary of the board.
24 P.S. § 2062