German silver keyless observation watch with regulator dial Circa 1945

Silver pocket lever chronometer 
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A very rare German silver keyless pocket chronometer pocket watch, circa 1945-1948. With a black regulator-type dial and Guillaume balance. A polished case and a hinged silver cuvette. Black lacquered dial with white Arabic numerals, outer minute track, subsidiary seconds at 3, hour dial at 9 and silver epee hands. A frosted gilt, three-quarter plate movement, 17-jewels, straight-line lever escapement with a gilt fork, Lange Guillaume balance, blued steel Breguet balance spring with patent stud fastening, and an index regulator. Dial, case and movement signed. Case with German silver mark.
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Diameter: 51 mm
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Signed: A. Lange & Söhne  Glashütte/Sa.
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The present watch is a rare model of a Beobachtungsuhr or observation watch with an unusual black regulator-style dial. This model was only made for three years between 1945 and 1948. An identical watch is illustrated and described in Die Uhren von Lange & Söhne, Glashütte Sachsen, Martin Huber.