To carry out the purposes of this chapter, the board is hereby authorized to issue negotiable coupon bonds of the district as herein provided. Bonds shall bear interest at a rate not exceeding six percent per annum, payable semiannually, and shall be due and payable serially, either annually or semiannually, commencing not later than three years and extending not more than twenty years from their date. The form and terms of said bonds, including provisions for their payment and redemption, shall be determined by the board. If the board so determines, such bonds may be redeemable prior to maturity upon payment of a premium, not exceeding three percent of the principal thereof. Said bonds shall be executed in the name of and on behalf of the district and signed by the chairman of the board, with the seal of the district affixed thereto and attested by the secretary of the board. Said bonds shall be in such denominations as the board shall determine and the bonds and coupons thereto attached shall be payable to bearer. Interest coupons shall bear the original or facsimile signature of the chairman of the board.