There’s a tendency for people to refer to expensive purchases asinvestments. “I’m going to investin a new TV,” someone might say. Yet televisions hold their value about as well as a Cosmo Kramer business idea holds oil. Televisions are not investments. Neither is a phone or a car, unless it’s a rare vintage one that will be kept in a garage and never touched.

Clearly, pretty much anything with a technological expiration date is a bad financial investment. This is why many skeptics have voiced concerns about the priciest Apple Watches–because it makes little sense to drop thousands of dollars on a gadget-fashion piece that will be outdated and lose value as time passes.

But what about mechanical watches? You know, the ones that don’t use electricity and are technologically static, immune from cutting-edge developments? People don’t buy mechanical watches for hi-tech features, so they’re not at risk of becoming obsolete.

Like wine, art, or other hard assets like diamonds, gold, and real estate, people sometimes do refer to watches as “investments” without completely misusing the word. And yet it would be silly to view a watch, or a collection of watches, as a core component of your investment portfolio.

“Don’t think about them as financial investments,” says Ariel Adams, the founder of ABlogtoWatch.com, a prominent horology website. “Buying low and selling high doesn’t typically work so well in the watch world.”

A large part of the reason, Adams says, is the fickle and emotional nature of the watch market. A single collector alone has the power to influence the tastes, trends, and values of the entire market. Pop culture plays a role too: There’s no doubt that James Bond propelled Rolex even higher when it debuted on Sean Connery’s wrist in Dr. No. Essentially, it’s really hard to predict where the market will go, even where tried-and-true marques are concerned, which makes watches troublesome as investment fodder.

Stephen Pulvirent, who writes about watches for Bloomberg, agrees: “If you’re looking for an easy, safe, blue-chip investment, put your money into a mutual fund.”

Part of this is because the ultra-high-rolling watch world may also be in the midst of a bit of a bubble, according to Adams, who points to the huge watch auctions that are reminiscent of the art world. But in the more down-to-earth watch market ($4,000-8000), the growth feels more meaningful.

So what watches best hold their value?

Certain relatively attainable ($4,000-$9000) watches are known to hold their value extremely well—even appreciating in some cases. Interestingly, they’re almost all made by Rolex. “I hate to say it, but in this price range, vintage Rolex—and now vintage Tudor, ‘the working man’s Rolex’—are the best game in town if you’re looking for an investment-grade piece that doesn’t have to sit in the safe,” says Adam Craniotes, a watch writer, collector, and founder of Red Bar, a group of watch aficionados.

Everybody seems to agree on this. “Along with Patek Philippe [a brand typically outside of this price range], it’s the only brand that is able to maintain the high resale value with the majority of its products,” says Adams. “Rolex has spent decades creating the marketing image that a Rolex watch is a sign of success—it also happens to be a good watch.”

Rolex’s dominance on the second-hand market is the reason why Altieri structures his whole business around a single brand. According to Altieri, “They’ve held their value the best. 90% of what Bob’s Watches does is Rolex. They dominate the new market and the old market.”

Not all Rolexes mature equally, however.

“In general the watches that have done the best over time have been the sport watches: The GMT, the Submariner, and the Daytona,” says Altieri, who chalks this up to the more casual nature of a watch designed for a job or use, not a formal occasion.

One of the reasons for Rolex’s success in value retention, according to Adams, is that it has kept the product line small, enabling many of these watches to become household names. Omega, in comparison, does okay on the second-hand market, but has hurt itself by peppering the field with so many different models over the years.