Clapper Post

Clapper Post (German: Klapperpost) was an urban postal service, which existed in Vienna (since 1772), capital of Austria, and in other cities of that country. Its name refers to an instrument, clapper (type of a rattle), into which a mailman struck, notifying about his arrival. In Vienna, Clapper Post existed more than ten years.^[1][2]

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  Clapper mailman (engraving; late 18th century)
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  A unique money letter with 50 florins in the form of banknotes from Prague to the town councillors of Ungarisch Skalitz (today's Skalica, Slovak Republic; 1783)

A seller and a clapper mailman (Vienna types around 1820)