What are Back of the Book Stamps?

Back of Book, Parcel Post, special Delivery Stamps Mint & Used Dealers Lot of 27

Back-of-Book Stamps

What's the value of this Scott's American Album for United States Stamps with 756 stamps installed have? (87 more miscellaneous stamps in the back) : r/stamps

Elizabeth Craft Designs Clear Stamp Set - Journal Phrases 2, CS305

Stamp Album Supplements

What are Stamps on Approval?

Netherlands - Back of the book wb. better Postal receipt, perforations, Postal parcel settlement stamps and - Catawiki

Embossed Envelopes, Postcards & Back-of-the-Book Stamps.

Worldwide Stamps Archives - Jamestown Stamp Company, Inc.

Canada ''Back of the Book'' Stamps Group US$30 post paid Reduced - STAMPBOARDS - Postage Stamp Chat Board and Stamp Forum