German spherical Melanchthon verge watch Circa 1530

The oldest pocket watch that still works
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The spherical Melanchthon watch from circa 1530. It belonged to Philipp Melanchthon, a colleague of the famous Christian reformer Martin Luther. It’s 48 mm in diameter, it would run between 12-16 hours on one winding, and it’s engraved in German translated to English, Philipp Melanchthon. To God alone the glory. 

It is not known who made the watch, because there isn’t any watchmaker’s mark. But it’s pretty clear that it’s made in Germany, and the spherical shape indicates that it most likely was made in the city of Nuremberg.
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Diameter: 48 mm
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First owner: Philipp Melanchthon
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What we do know, is that it must be incredibly valuable.