Twenty years ago, hiring a lab to help authenticate artwork was an expensive proposition. Today, it's a lot more accessible to ordinary buyers. Don't be afraid to ask a seller if you can get stuff checked out. The right test (radiocarbon dating, infrared photography, X-rays) can, for example, determine the age of paint samples or the chemical composition of varnish from a piece of furniture (if it comes back with formaldehyde, you'll know the finish isn't old). "If you're buying an expensive table or a Honus Wagner baseball card, there is a test available that will give you confidence to put your hand in your pocket," says Dowling. "Some of these tests are very simple, and there are places all over the country that can do them." And again, any reluctance on the seller's part is a red flag. "If someone turns you down, you're going to say, 'Right, then I've got my answer. Thanks for your time,'" Dowling suggests.