Section 7. Any co-operative association now organized by law in the commonwealth for any of the purposes mentioned in section three, and qualified so to do, may by a majority vote of the stockholders at a meeting called therefor vote to accept sections three to seven, inclusive, and shall thereupon present to the state secretary a certificate, signed and sworn to by its clerk or secretary, setting forth a copy of said vote, the date when passed, and such further evidence as the secretary may require of its legal existence and of its intention to accept said sections. The secretary shall examine the certificate and evidence of organization, and, if it appears that the law has been complied with, shall so certify, and shall approve the certificate by his endorsement thereon, and thereupon such corporation shall have the powers and privileges and be subject to the duties and liabilities of corporations formed under section three. Upon the payment of a fee to be determined annually by the commissioner of administration under the provision of section three B of chapter seven, said certificate shall be filed in the office of the state secretary.