After registration of a municipal bond as provided in section 21-03-34, no transfer thereof is valid unless made on the records of the county auditor or the records of the municipality by the registered owner in person, or by the registered owner’s duly authorized attorney, and similarly noted on the bond, but the same may be discharged from registration by being transferred in like manner to bearer, and thereafter transferability by delivery is restored, but such bond again from time to time may be registered or transferred to bearer as before. Such registration, however, does not affect the negotiability of the appurtenant coupons, but every such coupon continues to be transferable by delivery only and must remain payable to bearer.