Phosphorescent tagging was introduced in 1962 and was called Winnipeg tagging, since the city of Winnipeg was the first to test the new machinery. This tagging can be a little tricky to detect. For instance, when you shine a UV lamp on a Winnipeg-tagged stamp, you probably won’t see much. But, when you remove the lamp, an after-glow appears after a couple of seconds. Sometimes it is easier to just hold the stamp up and move it at different angles in normal light. The striping of the tagged bars can sometimes be detected with the naked eye as a subtle shading difference in the paper. The bars appearing slightly shinier or darker, depending on the observer.
Phosphorescent Winnipeg-tagging was the norm for 10 years. Then, in 1972, General (or Ottawa) tagging was introduced.
gefunden in:
Der Winnipeg-Phosphorstreifen-Aufdruck leuchtet unter der Prüflampe bläulich. Nach der Bestrahlung kurzes Nachleuchten.
Die erste dieser Marken erschien lt. Katalog am 13.1.1962 in Winnipeg.
Gruß kartenhai