Editing Postmark (section)

== Valuation of cancellations ==
The study of postmarks is a specialized branch of philately called [[marcophily]]. It may bring added value to the stamps by their historical significance. Other parameters are the rarity and the attractiveness. In particular, the stamps issued by the [[Empire of Austria]] during the 1850–1867 period (the 5 issues before the Austro-Hungarian compromise of 1867), are collected for their variety and beauty. More details can be found in [[Valuation of cancellations of the Austrian Empire]].
[[File:MährischOstrau 5kr 1878 MoravskaOstrava.jpg|thumb|Example of postmark with historical significance: bilingual in the Austrian monarchy Moravia province, 1878]]

A special or rare postmark can substantially add to the value of a stamp. For example, on a Victorian cover sold at auction for £8,000 in 2019, a [[two penny blue]] stamp "was upstaged by" a rare 'sun' date stamp.<ref>{{cite news |title=Auction Highlights: Great Britain 1841 London 'Sun' datestamp|work=Stamp Magazine |publisher=My Time Media |date=April 2019 |page=15|volume=85|number=4|issn=0307-6679}}</ref> Also, in addition to everyday postmarks there are postmarks indicating the [[first day of issue]] of a particular stamp and [[pictorial cancellation]]s commemorating local events, anniversaries, and the like' and slogan postmarks which advertise an event or pass information to the public (there has been a recent change to the term "pictorial postmarks" rather than "pictorial cancellations" by the USPS).

There are some examples of "faked covers" produced by philatelic forgers, most usually to increase their value, in which the postmark has been altered in some way; for example, by changing the date.<ref>{{cite web |url=http://www.askphil.org/b55.htm |title=How to be an Expert/Covers |work=AskPhil |publisher=Collectors Club of Chicago |access-date=March 17, 2009}}</ref>