The best inventions are often the simplest and, for simplicity and usefulness, philately’s greatest invention was the stamp hinge. The hinge wasn’t actually invented, rather it evolved. The earliest collectors just licked their mint stamps to put them in their albums and made a paste to gum down their used stamps. As the Nineteenth Century progressed, collectors started using the selvage of sheets to hinge in their stamps. It was only by the second and third generations of collectors that the need for an easy way to remove hinges was felt. Stamps that were gummed down in albums or hinged with gummed selvages were impossible to remove for trading or resale without damaging the stamp or at least the gum.
Small pieces of paper were gummed and sold as hinges, but the first generation of hinges were gummed pieces of porous paper that stuck to the stamps they were hinging and were not much easier to remove than the gummed pieces of selvage they replaced. Later hinges used gummed pieces of glassine, a paper that is not porous, so that the gum of the hinge stuck lightly to the stamp, making it easy to remove. I don’t believe that there are any stamp hinges commercially manufactured in the United States anymore. This is a shame as it makes general worldwide collecting difficult. Hinges were an inexpensive and easy way to mount stamps. Commercial plastic mounts are expensive and difficult to use. Certainly they are necessary with scarcer stamps, but more trouble than they are worth with more common items. The demand for old fashioned hinges still exists and can be seen on eBay, where old unopened packs of Dennison hinges with the price preprinted on the package (1000 hinges for 25c) now sell for as much as $5 a pack