Section 15. In prosecutions for forging or counterfeiting a note, certificate, bill of credit or other security issued on behalf of the United States, or on behalf of any state or territory, or for uttering, publishing or tendering in payment as true such forged or counterfeit note, certificate, bill of credit or security, or for being possessed thereof with intent to utter or pass the same as true, the certificate under oath of the secretary of the treasury, or of the treasurer of the United States, or of the secretary or treasurer of any state or territory, on whose behalf such note, certificate, bill of credit or security purports to have been issued, shall be admitted as evidence for the purpose of proving the same to be forged or counterfeit.