Top billing goes to an early cast of , which has been in a private collection in Detroit since 1961. This version was cast in 1905, 12 years before Rodin's death, and its previous owners can be traced back to 1917. It is smaller than the one sold in New York.

Of the eight Rodins on show, three are lifetime casts of , another iconic sculpture, and two are early versions of . Rodin kept all the moulds and plaster casts made from clay and plaster models that he personally worked on. Before his death, he left everything he owned to his country on the condition a museum was established to display his work and manage his legacy.

This may have been great for the art world, but not so good for collectors since identical copies can be created indefinitely. "Since its creation in 1919, the Rodin Museum has produced about 5,000 bronze casts of various subjects within the limit authorised for each of them by French law," says Jérôme Le Blay, the Paris-based Rodin expert who authored the preface to the exhibition catalogue.

"These works made by the artist's estate are original casts and they are sold through the world's major art dealers and auctioneers," adds Le Blay, who is helping to compile the most comprehensive catalogue of Rodin's work ever attempted.

Later "original" casts, authorised reproductions and outright fakes, are distractions to serious collectors who will pay top dollar for an iconic subject that was cast during the artist's lifetime, is in excellent condition, and boasts a perfect ownership record.

"Most of the gallery exhibitions that we have seen in recent years consisted of recent casts," says de Sarthe, adding that and both versions of are being shown in public for the first time.

"Never has a gallery in Hong Kong had an exhibition of lifetime casts by Rodin."

De Sarthe Gallery, 8/F Club Lusitano Building, 16 Ice House Street, Central. Until June 22. Tue-Sat, 11am-7pm, free. Inquiries: 2167 8896