Wis. Stat. § 408.206: Completion or alteration of security certificate.

(1) If a security certificate contains the signatures necessary to its issue or transfer but is incomplete in any other respect:

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

(b) Even if the blanks are incorrectly filled in, the security certificate 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.