I visited the exhibition from Van Cleef & Arpels in Paris (Les arts décoratifs). You can see more than 500 pieces that have perpetuated the renown of Van Cleef & Arpels since 1906. These prestigious creations are completed with archive documents and drawings.
You can find
here (virtual tour of the workshops at Van Cleef & Arpels) how these jewels are fabricated nowadays at Van Cleef & Arpels. It gives a good impression of the different stages.