An ‘Antiques Roadshow’ appraiser reveals which early American cookbooks and old appliance recipe pamphlets are your best investments.

Before you throw your old cookbooks away, it might be worth getting them appraised.

Antiques Roadshow’s latest season, which premiered this past Monday, will make a stop in one of America’s most beloved food cities: New Orleans. While shooting in the well-known southern travel destination and former Louisiana capital’s convention center last summer, Antiques Roadshow appraiser and Brattle Book Shop owner Ken Gloss revealed to Forbes that our old family cookbooks are worth more than we realize.

Gloss calls the world of cookbooks “a vast field” where items are growing in value. But you should know that not everything you’ve been keeping on your kitchen counters and bookshelves is going to fetch you a pretty penny. Collectors aren’t really after what you’re probably using regularly, like cookbooks from high profile chefs Ina Garten and Anthony Bourdain, or celebrity chefs Chrissy Teigen and Gwyneth Paltrow. Instead, your hidden investments will come from specialty cookbooks you’ve tucked away in your basement or attic.

According to Gloss, some of the earliest American cookbooks (dating back to the 1790s) are selling in the $1,000 range, while books from as far back as the 1400s and 1500s go for thousands of dollars. Some other pricey collectibles are glossy cookbooks about cake decorating from the 1920s, first editions signed by cooking legends like Julia Childs and Fannie Farmer, and even some hard to find recipe pamphlets once included with newly purchased appliances. Gloss states that although seemingly mundane, their high price tag is due to how these items serve as historical documents—about places, people, cultures, and, of course, the food of the time.

“[Cookbooks] offer a view into society at the time,” Gloss told Forbes. “What were the foods people were eating? What was available? How were they preparing them?"

So what happens if you’ve found a cookbook, but it has some wear or tear? Fear not. While butter stains might depreciate the value of a first edition from Charles Dickens or Virginia Woolf, when it comes to cookbooks, collectors know these books were often used, so stains increase the aesthetic appeal while also serving as a way to confirm their authenticity.

To see for yourself how much some of these cookbooks go for, you can tune in to this season of Antiques Roadshow, airing Mondays at 8 p.m. ET on PBS, or apply for tickets to the 2018 tour of the U.S. online.