To jump into the used watch market is to swim in murky waters. Many pawn shops don't have professional appraisers on staff, and eBay and Craigslist deals are often scams. That's why Hamilton Powell founded Crown and Caliber, an Atlanta-based company that helps people safely buy and sell pre-owned watches online. His secret weapon is a team of in-house valuation experts who price each piece based on a database of historical sales records.

"We can tell you how much a watch sold for decades ago, online, at auction, at a dealer, and so on," Powell says. "It's an important step to getting your money's worth, and to make people feel like they're not getting ripped off."

Unfortunately, there isn't always going to be an appraiser on hand when a vintage watch catches your eye. You'll want to get an expert opinion before you take out the checkbook, but that opinion is going to cost as well. Here are the questions you need to ask before you call Powell or your local expert.

Is it rare?
Is the piece one of 100, or one of 10,000? The difference is key. "We're consigning a Jaeger LeCoultre watch that is one of 35 ever made," Powell says. "It retailed for almost $200,000." While there is no Kelly Bluebook for watch values, interested buyers can try looking up similar models on eBay and on other watch sales sites like Bob's Watches for comparisons. Just be careful not to confuse rare with undesirable. If you only find one on the market and the price is low, it's more likely that its the latter.

What condition is it in?
The vintage watch market is a lot like the used car market. "It can be waxed and cleaned, but if the engine isn't running right, it's a tough sell," explains Powell. Crown and Caliber employs watchmakers that take apart each timepiece for lubricating and pressure testing to make sure it's functioning properly. "It cranks the value way up," he says. Ask pointed questions about what maintenance the watch has undergone so you don't get stuck with those problems. 

What are your watches complications?
Watches can have a lot of bells and whistles, including perpetual calendars, minute repeaters, and power reserve functions. What, besides telling time, does the watch do? "The more complications, the more it's worth," he says. That means that just because you find a certain functionality to be excessive, doesn't mean it should be overlooked.

What is the brand's reputation?
Watches made by a handful of elite brands hold their value better than others. Brands like Rolex and Patek Philippe tend to stay valuable longer, while "blinged-out fashion watches lose value over time," Powell says. A rule of thumb: If the watch is more about the exterior than the interior, it's not going to stay valuable.

Do I love it?
Luxury watches aren't just an investment. You should want to wear every timepiece you own. If you don't feel strongly about a piece, keep moving. There are lots of very shiny fish in this sea.