These days, vintage watches are hot enough that some aficionados treat their collections like 401(k) accounts: a great way to build for retirement. But with prices spiking, the level of risk is shooting up, too. Even experts can get stuck with bad merchandise if they are not careful. Eric Wind, a vice president and the senior watch specialist at Christie’s New York and a longtime contributor to Hodinkee, the watch blog, discussed the new rules of buying vintage.

What is driving the vintage watch boom? There are two main factors: scholarship and social media. By scholarship, I mean blogs like Hodinkee, collector forums and auction houses. Instagram has also drastically changed the field. Watch-collecting used to be a private affair, but now you have tens of thousands of watch collectors showing off their watches and millions of people following them.

What is that doing to the market? There are so many more people chasing vintage watches today, particularly in that sub-$10,000 price category, and prices on some models have jumped many times in value in just a few years. I remember two pretty nice Universal Genève “Nina Rindt” Compax chronographs from the 1960s that sold for $2,310 and $2,550 in 2011 on eBay. In our December auction in New York, we sold one for $47,500.

Is it crazy to buy a vintage watch on eBay? For someone with little to no knowledge, it is the Wild West. Many people falsely believe a 100 percent feedback means a seller is legitimate. For some reason, many of the most egregious sellers of fake vintage watches have feedback history of 100 percent after hundreds of transactions, perhaps because people buying the watches did not know what they were buying. Still, once you have more advanced knowledge, eBay can be a great source for vintage watches, particularly in the lower end.