Already, some sure things, like certain Daytonas, are looking like slightly less than a sure thing.

“The market for Daytona just got a little silly for awhile,” Mr. Clymer said. “We saw references worth $20,000, $25,000 in 2011 to 2015 all of a sudden worth $50,000, then all of a sudden worth $80,000. And now those same references are worth $65,000. That’s still significantly higher than they were, but they’ve come down from the stratosphere.”

During the bear market of 2008 to 2009, too, prices for some high-flying vintage models, including Paul Newmans, dipped by 30 to 40 percent, said Matthew Bain, a dealer of fine watches in Miami Beach. But, like stocks, they bounced back to new highs.

The rebound may seem intoxicating. But people who think of their watch collection as an alternative to an E-Trade account may be in for a rude surprise when they discover that watches often come with sizable dealer fees, not to mention substantial outlays for insurance, secure storage and other hidden costs, Mr. Khoo said.

“Investors are not collectors, and collectors are not investors,” Mr. Khoo said. His Watch Fund has a database of “more than 9,000 watch collectors worldwide,” he said, and “I have never met someone who bought hundreds of watches that he liked, and sold 100 percent of them for a net absolute gain.”

In other words, newcomers to the watch world may want to heed the warning attached to brokerage advertisements on television: Past performance is no guarantee of future results.

Or, they may just want to buy whatever looks cool and leave it at that.