The trial has opened in the western city of Neuchâtel into a scandal that rocked Switzerland's watchmaking industry five years ago.
The 15 people on trial are facing charges that include theft of gold, handling stolen goods, forging watches, robbery and possible extortion. Two, who live abroad, did not appear.
The complex case which includes some of the leading watch groups as plaintiffs - Rolex, Richemont, Cartier and Frank Muller - is set to last five weeks.
Some of the accused are also charged with two armed robberies in which 52kg of gold were stolen in June 2002 from companies in La Chaux-de-Fonds and Le Locle.
The scandal came to light after watch movements factory owner Jean-Pierre Jaquet was arrested in October 2003 on suspicion of robbery, handling stolen goods and forgery. It caused an uproar in Swiss watchmaking circles.
"It's like a bunch of cardinals getting together and robbing the Vatican bank," commented Nicolas G. Hayek, chairman of the Swatch Group.
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