Proof of disability shall be made by exhibiting a federal government rated disability certificate to an extent of 25 percent or more, or an affidavit from an examining physician of the United States Veteran’s Administration showing that the applicant for license is physically disabled to the extent of at least 25 percent or by the production of a pension certificate issued by the United States Government or by the State of Alabama or by a certificate of the county health officer of the county in which the veteran resides or, if there is no county health officer, a certificate by a reputable physician in the county in which the veteran resides, said physician’s certificate to be attested before some officer authorized to administer oaths.