This brooch made 1912 by Josef Hoffmann is estimated at €150,000-300,000 at Dorotheum in Vienna on May 30.

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Alongside a pendant set with semi-precious stones, made in an edition of three in 1903-04, which is estimated at €90,000, a unique brooch made before 1912 is expected to take top honours.

The floral design of the 1.6 x 1.6in (4 x 4cm) brooch, which was executed by the Viennese goldsmith Karl Ponocny, incorporates gold, mother-of-pearl and moonstone and comes with its original leather case.

For the last nine years it was on loan to the Jewellery Museum in Pforzheim. Now, its owner has consigned it to Dorotheum where the estimate is €150,000-300,000.