Dear Lee,

You are too young to remember the cardboard grocery store we gave you for Christmas. It took your parents most of the night to “build” it and put all the boxes of cereal and sugar and tea together so you could stand behind the counter and play store. When you saw it the first time, you glanced at it and didn’t go near it again for weeks. It wasn’t your favorite plaything, but we thought it was great. Too bad we didn’t save it. Each little brand-named box would sell for about $15 today, and the playhouse-size store is worth close to $100.

Think about the gifts you should save this year because they’ll be the collectibles of the future. Many things determine value: age, supply, condition, lovability, fame of the person or thing made into the toy, connection to a TV show or movie and whether the toy works.

Any Barbie doll could still be considered collectible, but the one to keep pristine in her box for the future is “Totally Stylin’ Tattoos Barbie,” already in short supply.

Timing is everything. Toy collectors want the toys of their childhood. The O-gauge trains like Lionel, originally popular in the 1920s, were still-remembered expensive collectibles in the 1950s; now they’re lower-priced because collectors want the later HO scale. Mr. Potato Head, first sold in 1949, was unimportant until the Toy Story movies reintroduced him. Now early versions—those that required a real potato, those with a pipe, those with feet but no legs—are pricey collector’s items.

In the 1960s, Danish toymakers made modern-looking wooden animals, including monkeys with long arms that could hang in a chain and a sleek elephant with moveable arms and legs. Today those toys are wanted as decorations in modern homes, and each sells for $200 or more.

Celebrities like Charlie Chaplin, Tom Mix and Shirley Temple are almost forgotten today, so their toys attract few buyers. Robots, space toys and superheroes go up in price as they age, so fewer and fewer can be found. But like teddy bears and Raggedy Ann dolls, new space and superhero toys are enough like old ones to evoke memories. Keep Hot Wheels toys and their original packages. Collectors still want every one, old or new. Don’t bother with Cabbage Patch dolls, most paper dolls, View-Masters or most board games.

Will Harry Potter character toys be wanted in 20 years? It depends on the future marketing of the books and movies. Most played-with electronic toys will be unwanted after the electronics stop working. No one wants a talking toy that has lost its voice. If you find a playhouse-size grocery store, like ours but probably made of plastic, you might want to give it away when your children outgrow it. I doubt if it will sell for much even 25 years from now.