Some of the cookie jars had animal designs, including cats, ducks and cows — signifying cookies and milk. Others were shaped like apples. Some just had the word “cookies” on them.

Here’s what to watch for. A cookie jar can be valuable for all sorts of reasons: age, condition, brand, shape and rarity. Here are some finds that have proven lucrative in recent years.

Cookies and biscuits easily absorb moisture when unwrapped. So, to keep them crispy, they can easily be stored in jars. Available in different sizes, shapes, designs and materials, selecting the ...