Graphite lined stamps were used in the United Kingdom from 1957 to 1960 as an experiment in the automation of mail sorting.
[1] In the United Kingdom, graphite lines were used exclusively on five stamps of the Wilding series from December 1957.
[1] Several other errors of misplaced graphite lines are also known and not all are included in the Stanley Gibbons catalogue.
The machine used scanners to detect the graphite lines and to face the letters so that the stamp was always in the top right corner.
This has attracted forgers, however, most forgeries are easily identified by comparison with a genuine stamp.