In Diana (Saint-Gaudens), how is the Busts and heads of the Other versions elucidated?
In 1908, the sculptor's widow authorized a posthumous casting of nine busts based on Saint-Gaudens's 31-inch (78 cm) statuette. A 7-3/8 in (18.7 cm) plaster bust is at Saint-Gaudens National Historic Site.  Bronze busts are at the Carnegie Museum of Art, and in private collections.
Bronze casts of Diana's head are at Saint-Gaudens National Historic Site; Harvard University; and elsewhere.
Harvard University Carnegie Museum of Art Diana Saint-Gaudens National Historic Site