(1) If a security certificate contains the signatures necessary to its issue or transfer but is incomplete in any other respect, it may be completed as follows:

    (a) Any person may complete it by filling in the blanks as authorized.

    (b) Even though the blanks are incorrectly filled in, the security as completed is enforceable by a purchaser who took it for value and without notice of the incorrectness.

    (2) A complete security certificate that has been improperly altered, even if fraudulently, remains enforceable, but only according to its original terms.