How can I check if my old Apple Gift Card rewards are valid?

A number of years ago, Apple would give you a $25 rewards card with a scratch off number on the back of the card every time you spent a certain amount of money at the Apple store. I have just found two $25 cards that I have had for a number of years, are these still valid?

[Re-Titled by Moderator]

Original Title: Old Apple Rewards Cards