Section 30. Negotiable Documents of Title Marked "Not Negotiable."—

If a document of title which contains an undertaking by a carrier, warehouseman or other bailee to deliver the goods to the bearer, to a specified person or order, or to the order of a specified person, or which contains words of like import, has placed upon it the words "not negotiable," "non-negotiable" or the like, such a document may nevertheless be negotiated by the holder and is a negotiable document of title within the meaning of this act. But nothing in this act contained shall be construed as limiting or defining the effect upon the obligations of the carrier, warehouseman, or other bailee issuing a document of title of placing thereon the words "not negotiable" "non-negotiable," or the like.