Sorry, but that probably isn't Cleopatra's coffee mug.
Credit: Getty Images

Some of the riskiest purchases are ordinary objects that are supposedly connected to famous people or important events. Most of the time, there's just no way to definitively verify provenance. "This is probably one of the biggest frauds of all time," says Dowling, "because isn't every pair of glasses the one that John Lennon was shot in? Isn't every tea bowl the one that Hirohito drank out of before he renounced his divinity? If you hear a story that sounds too good to be true, it probably is." In other words, don't ever just take somebody's word for it. If something's valuable just because of who once used it, then you're taking a huge gamble. You're much better off investing in something that's valuable because of what it is (a Rembrandt!), not because of who purportedly once owned it (Babe Ruth's dirty socks!).