Any H bonds and Savings Notes that are more than 30 years old no longer pay interest. Those old savings stamps are still worth something. When enough were accumulated, they could be traded in for a bond. Today, the stamps are worth exactly what you paid for them, redeemable at the Federal Reserve Bank office serving your area for cash. Or buy a bond with them by supplementing the difference between what you have and a bond's purchase price.
Bonds issued within days of each other can pay vastly different rates.
Because each bond is subject to the guarantees in effect when it was issued, you need a government chart to see what is what. Click here for more information about savings bond interest rates. Lost, stolen or mutilated bonds can be replaced. As long as you can establish that your bonds are indeed missing or that an unauthorized person has cashed them, you can get the Treasury to issue you new ones. It's important to keep a record of your bonds and their serial numbers so you will know what to list on a claim form later.