All revenue bonds, the issuance of which was authorized or ratified at a general or special election held within the issuing jurisdiction prior to July 1, 1970 or the proposition for the issuance of which will be submitted at such an election pursuant to action of the legislative authority of the issuer taken prior to July 1, 1970, may be sold and issued with an interest rate or rates greater than any interest rate restriction contained in the ballot proposition or ordinance or resolution relating to such authorization or ratification.