Any such general obligation bonds or revenue bonds shall be executed in the name of and on behalf of the municipality and signed by the chairman of the board, mayor of the city or other titular head of the municipality with its seal affixed thereto and attested by its clerk. Except for such bonds which are registrable for payment of interest, interest coupons payable to bearer shall be attached to the bonds and shall bear the original or facsimile signature of said two officials. The bonds and coupons bearing the signatures of the officers in office at the time of the signing thereof shall be the valid and binding obligations of the municipality, notwithstanding that before the delivery thereof and payment therefor any or all of the persons whose signatures appear thereon shall have ceased to fill their respective offices.