Oil painting from the 19th century, showing the <i>Bremer Tonne</i> (“Bremen bouy”) or <i>Schlüsseltonne</i> (“Key buoy”) north of the sand bank <i>Roter Sand</i> (“Red sand”), first established in 1664 to mark the route to the estuary of the Weser river.
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Unknown author<span style="display: none;">Unknown author</span></div>
19<sup>th</sup> century <div style="display: none;">date QS:P571,+1850-00-00T00:00:00Z/7</div>
Herbert Schwarzwälder: <i>Das Große Bremen-Lexikon</i>. Edition Temmen, Bremen 2003.