German full hunting case pocket watch made of 900 silver Circa 1903

Extremely rare Glashütte silver pocket watch
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A solid full hunting case pocket watch crafted of 900 silver and made for Billian Fils in Zürich, Switzerland by A. Lange & Söhne in Glashütte, Germany, circa 1903. The watch has a silver full hunting case, a stepped enamel dial with the seller’s signature “Billian Fils, Zürich” and red gold hands and a movement with a rare escapement according to Patent number 26139.
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Diameter: 52.5 mm
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Weight: 116 g
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Signed: Billian Fils, Zürich
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The watch and its probable history is described in detail in Chrono-Hype issue 3, p.26+27, Stefan Muser/Dr. David Seyffer, curator of the IWC Museum and Reinhard Reichel, former curator of the Glashütte Watch Museum. Accordingly, this watch was originally delivered to the company Billian Fils Zurich with a gold case. It is believed that this gold case was later melted down. In the Lange archive, there are 5 verifiable entries that Lange & Söhne made cases for existing IWC movements. This seems to be a 6^th example of these Lange watches with third party movements, an absolute rarity!