Caught In The Mail: Using A "Muster" (Specimen) As Postage A Month Early!

Hi everyone,

My daily sorting turned up another really unusual piece today, and I thought the postal history fans here would get a kick out of the clerk's reaction on this one.

This cover has a 20pf stamp for the 100th birthday of Nathan Söderblom (the Swedish Protestant theologian and 1930 Nobel Peace Prize winner). The catch is that the stamp has a "Muster" (Specimen) overprint. It was clearly an advanced reference copy meant for postal branches or the press, making it completely invalid for postage.

What really caught my eye was the timeline. According to the catalogs, the official issue date for the Söderblom stamp wasn't until January 15, 1966. Yet, whoever sent this managed to get their hands on the specimen and drop it in the mail on December 16, 1965—an entire month before the stamp even existed to the public.

The postal clerks in Bonn were definitely awake that day. They immediately caught the discrepancy, boxed the invalid stamp out in blue pencil, and refused to cancel it. They postmarked the envelope directly instead. Because it was treated as unpaid, they hit the envelope with a massive blue "50" to collect 50 Pfennig postage due (Nachporto) from the recipient, backing it up with a red "Nachgebühr" handstamp the following day.

Has anyone else come across specimen stamps successfully (or unsuccessfully) slipping into the mail stream like this?