If you want to buy a vintage watch, eBay is both a blessing and a curse. On the one hand, you can usually find what you’re looking for — even if it’s obscure — and you can usually score it for a decent price. On the other hand, it’s filled to the brim with what’s perceived to be a scourge upon the vintage watch community: the Frankenwatch.

The term ‘Frankenwatch,’ gets thrown around a lot, often as a catchall to describe a watch that isn’t in original condition, or possibly has faked components. But that’s turned it into something of a misnomer. “To me, a Frankenwatch is cobbled together with often real but not necessarily correct parts,” says Nick Pardo, previously a vintage watch expert at Analog/Shift, which specializes in accessibly-priced timepieces. “So you have a dial from one model, hands from another, and it’s built up from random parts.”

Often found through online auction and classified sites like eBay, Frankenwatches persist mainly on the low end of vintage watches. This isn’t to say they aren’t an issue with rare or higher-end watches, but Frankensteined versions of vintage Seiko sports watches and Omega Seamasters, for example, are so common because the watches they’re based on were ubiquitous in the first place. “They aren’t completely modular, but they’re close to modular, so they have a lot of parts that are easy to interchange,” says Pardo. “For example, Omega had the 500-series movements in tons of watches, so any hands that fit those models would work on any other. You can get a movement that fits a case, and then you can get a set of hands that came on any one of those watches over a 30-year period and slap them on there.”

So a Frankenwatch, in the truest sense, isn’t one that’s been faked or a genuine watch that’s had a part replaced. Instead, think of it as a watch that’s been put together in a configuration that would have never come from the factory. Collectors often frown upon these because in watch collecting — like in vintage car collecting — buyers overwhelmingly want to own a piece that’s as close to the watch that originally came out of the factory decades ago. As such, having a full original watch means you can command a higher price on the vintage market.

But here’s the thing: an unoriginal Frankenwatch can often be had at a lower price, and in decent shape, to boot. Think of a classic car that’s had an engine swap, or has been fitted with aftermarket parts over the years to keep running. It may not garner a higher premium at auction, but at the end of the day, you can have a fun, good-looking machine that functions. And since a Frankenwatch is unlike any of the watches originally manufactured en masse, your piece is more unique. What’s wrong with any of that?

Well, nothing inherently, but the problem with Frankenwatches is that their sellers are often less than forthright. “When they’re not disclosed, I think that’s really what gives them the bad name — when people try to command the same price as an original piece,” says Pardo. Given that, whether or not you’re looking for an original piece, or you’re okay with owning a Frankenwatch, being able to spot one is key to getting the best value for your money.

Since Frankenwatches often are using factory parts, it can be tricky to tell what’s legit and what’s not. Pardo says if you can find a reference number on a listing use that and then check it either with vintage databases (like Omega’s) or simply comb through Google searches to see what’s supposed to be correct. Another easy way for a novice to find out if a piece is a Frankenwatch or not is to go to Instagram or a watch forum and ask for help. “People know their stuff there so they can tell you pretty quickly,” he says.

So if you know a watch is Frankensteined and you’re okay with that, buy to your heart’s content so long as “you know what you’re getting and you’re paying a fair price — which should be really low,” says Pardo. Be prepared for the possibility that that watch might stop running and that it might not be worth repairing. “The cost of repair will often exceed the actual value of the watch, as with any other low-cost vintage watch. If you buy something for $200 and need any part to get it up to snuff it just might not be worth it.”

Still, it’s all part of the journey that makes being a collector exciting. The low cost of a Frankenwatch means that finding and acquiring new vintage timepieces becomes cheaper and thus easier, and the intensive research required in confirming a watch’s legitimacy (or illegitimacy) will put you well on your way to becoming an expert. Some collectors may continue to look down on them, but disregard their sneers and enjoy that unique and cheap little machine on your wrist.