For example, Shreve & Co:
"For some, watches are purely functional. You look at them, the time is more-or-less correct, and you tuck it back under your sleeve."
That was 50 years ago. Today, those people don't have watches at all. If they need to know the time they look at their phones.
They go on to tell you that, judging from current auction activity, a high-quality watch, a watch which is much more than a timekeeper, could rise in value 30 to 40% over 10 years.
30 to 40% in 10 years, as a best-case scenario, is not a great investment. There are mutual funds that will just about guarantee that sort of return as a worst-case scenario.
Real estate is an investment. But fewer people care about watches than they did decades ago, whether as a purely functional timekeeper, or a neat gadget which is fun to have, or as a hand-crafted luxury item which is a thing of beauty, or any which way. And there's no indication that that trend is about to reverse, and that in the future more people will wear and/or collect watches. Fewer people being interested in watches in any way means fewer customers competing to buy them, which means that their prices are more liable to go down as they age, than up. And that's as true for a luxury watch you buy today, as for a cheap piece of junk.
You can rack your brains and study and study, and maybe you'll end up buying one of those watches which will rise 30 or 40% in the next 10 years. Or you can make a no-brainer decision on a mutual fund and beat 40% easy. Or you could buy a building or some land, take a risk and maybe some upkeep headaches as well, but there's a very good chance that you could clean up.
The only good reason to buy a watch is the voice in your headache that keeps screaming that you have to have it. Don't have such a voice in your head? Then don't let someone tell you watches are a good investment. If you do love watches, you should get the one you love -- not the one someone tells you is a good investment, and also not the one that someone else, who you're afraid is much cooler than you, tells you is the coolest one, but the one which you like the best.
Now, it's possible that your family have been manufacturing and selling fine watches for over 300 years, and that you know far more about watches than I could ever learn in 20 lifetimes, and that, besides watches themselves, knowledge of watch markets and booms and busts in those markets, and knowledge of the psychology of watch buyers, is in your very DNA. If all of that is true of you, then for you, quite possibly, watches, which you buy and hold onto for years or decades because you know their prices will skyrocket, could be a good investment. But if you're that person, you certainly didn't need the likes of me to tell you that for most people, a plan to amass wealth by buying Rolexes and Patek Phillippes, or antique watches of one brand or another, is just plain silly.