Unless they have marks, it will be difficult to determine maker. Of all bookends made, the ship has to be more plentiful than any other. Seems that all makers made ships in many styles.
Yours are listed in McBride's book, 1997 as Galleon, Bronze, 4.25"x3.5", $30-$50, with no maker listed.
They will also be found in cast iron. Magnet will attract to cast. Many bookend molds were bought up by other companies and re-cast over the years.