According to the FBI’s website, organized groups of thieves often use intermediaries, commonly called fences, in cities such as Los Angeles, Houston, New York and Miami to convert stolen goods into cash.

In his case, Mr. Harris said, authorities have leads to two fences in Miami. “We suspect a Miami jeweler and a known Milanese money launderer, identified in the Rio hotel’s surveillance video,” Mr. Harris said. “In the U.S., the hub for stolen watches is Miami. In Europe, it is Italy.”

There are no official statistics on the number of watches stolen around the world each year but the FBI’s website estimates that the jewelry and watch industry in the United States loses more than $100 million annually in retail thefts. Since 1992, the FBI’s Jewelry & Gem Theft program has helped the industry combat such crimes. And, while the bureau does not maintain a database, it does cooperate with the Jewelers’ Security Alliance, a nonprofit trade association that has a registry of stolen watches and jewelry.

In Europe, Europol, the European Union’s law enforcement agency based in The Hague, offers similar help to businesses and it works with International Jeweller Security, a registry site.

After the robbery, Mr. Harris posted descriptions of his watches and their serial numbers online. That information was picked up by MyStolenWatch, a specialized theft-check website that, like Watch CSA or WatchFacts, lists stolen watches by serial numbers. “My watches and their serial numbers are now listed on several registers and they also come up in a Google search if anyone checks,” Mr. Harris said.

The theft-check company with the largest global database of stolen watches is Watch Register, a London-based site operated by the Art Loss Register, a well-known stolen art tracking service founded in 1990. The Watch Register provides both identification and recovery services of lost and stolen watches across borders.