ZURICH --- Swiss watches are in high demand these days, but sales of secondhand timepieces are also booming, driven by Generation Z buyers who want luxury goods but are also sustainability-minded. The global secondhand watch market is estimated at nearly 20 billion Swiss francs ($21.7 billion) and could reach 35 billion francs by 2030, according to a study out in October by the auditing and consulting giant Deloitte. Historically the province of collectors scouting for rare watches at auction, the secondhand market is turning increasingly professional with the proliferation of online sales sites that verify authenticity---with even the watch manufacturers themselves getting inv...Keep on reading: Generation Z finds time for secondhand watches