However, alterations on the reverse side of the stamp required physical examination of the item in order to see a regumming, a covered thin spot or an enclosed tear. Some auction descriptions may state the nature of the repair. Here is a good example of why previous auction catalogs are important. In 1980, a block of four of the 5-cent stamp of the first issue of the Netherlands was offered for sale with an abrasion between the bottom two stamps. A sale in 1982 offered the same block with an ink spot between the two stamps.
Postal forgeries abound throughout the world.
Some are outstanding cases of the work of an artist. Technically, these stamps are not forgeries since they never existed but were created and accepted in the philatelic community. Another common stamp forgery is false or enhanced overprinting. An overprint may be very light, or possible non-existent, and the skilled artisan can fill it in so that there is no question of the nature of the overprint. Some of the early overprint forgeries were crudely done using type similar to the original.