The post office identity cards, introduced on June 1, 1904, were issued upon application to each post office for a fee, and were valid at all German post offices as well as in most European and many non-European countries. They acted as proof of the holder's right to receive documents. It could also be deemed as a form of identification at the Post Office counter. In 1920 the issuing of postal identity cards was also included in the regulations of the Universal Postal Union.
This postal identity card with the number 6 on was issued at the Lübben / Spreewald Post Office and was valid until June 30, 1935.
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