CREATE TABLE table_17728 ("Ship" TEXT, "Builder" TEXT, "Namesake" TEXT, "Renamed" TEXT, "Laid down" FLOAT, "Launched" TEXT, "Commissioned or completed ( * ) " TEXT)

What is the namesake of the ship that was commissioned or completed(*) 16 april 1864?
SELECT "Namesake" FROM table_17728 WHERE "Commissioned or completed(*)" = '16 April 1864'
SELECT "Namesake" FROM "table_17728" WHERE "Commissioned or completed(*)" = '16 April 1864'