Definition: Back of the book are those stamps which are found in the back of most specialized stamp catalogs. It includes most of those stamps which are not the primary postage stamps issued by a postal authority (commemoratives and definitives). Specific definitions can vary, some consider airmail as being back of the book while others do not. Some of the types of stamps that are typically considered back of the book include:
- Special Delivery Stamps
- Postage Due Stamps
- Revenue Stamps
- Newspaper Stamps
- Official Stamps
- Airmail Stamps
- Duck Stamps (or similar wildlife permit stamps)
- Postal Stationery
- Semi-postal stamps