Bonds issued may be either registered or coupon bonds.  Coupon bonds may be registered as to principal in the holder’s name on the books of the financial officer of the subdivision after the registration has been noted upon the bonds by the financial officer, no transfer shall be valid unless made on the financial officer’s books by the registered holder, and similarly noted on the books.  Bonds registered as to principal may be discharged from registration by being transferred to the bearer, after which they shall be transferable by delivery, but may be again registered as to principal as before.  The registration of the bonds as to principal shall not restrain the negotiability of the coupons by delivery.