Editing Cancellation (mail) (section)

==Forgeries==
{{main|Philatelic fakes and forgeries}}
Forgers have not only manufactured stamps for the philatelic market but also added forged cancellations to those stamps. This was especially common in the late 19th century and the early 20th century, when huge numbers of inexpensive stamps were forged for the packet trade.<ref>See generally, [[Robert Brisco Earée|R.B. Earée]], ''Album Weeds; How to Detect Forged Stamps'' (3d Ed. reprint, Manuka-Ainslie Press, Acton, Canberra n.d.).</ref>

Forged cancellations have also been applied to genuine stamps if the stamps are worth much more postally used. In addition, if rare cancellations are desired by collectors, those cancellations have also been forged.

Cancellations may also be used to prove that certain philatelic items are genuine.  For example, forgers have fabricated many supposedly-valuable postal covers by adding genuine stamps and forged postal markings to pre-stamp covers.<ref>See, e.g., Jean-François Brun, ''Out-Foxing the Fakers'' (American Philatelic Society, State College, PA 1993), Chapter 6.</ref> A cover can be shown to be genuine if a genuine cancellation "ties" the stamp or stamps to the cover or, in other words, if a genuine cancellation runs continuously over the stamp and adjacent portion of the envelope. However, one still may need to rule out the possibility that the cancellation was added later. Similarly, stamps that were cut in parts and used for a portion of the full value as [[Bisects and splits (philately)|splits]] can be shown to have been so used only if a genuine cancel ties the stamp to the cover or piece of cover.