One of the most popular hobbies of the baby boomer generation was stamp collecting. Many people collected stamps as it was generally a inexpensive hobby and were easily accessible through the local post office.
Stamps, used and unused have value. Never remove stamps from the original envelope before showing us. Many have more value on the original envelope it was mailed on than if it is soaked or pulled off.
Both canceled (used) and uncanceled (unused or mint) stamps have value (USA or Foreign). Stamps were also used for revenue purposes on documents (deeds, stocks, wills, etc.) hunting licenses, medicine, business licenses, permits and many more ways.