German silver lever deck watch with power reserve Circa 1942

Silver open faced lever with power reserve by A. Lange & Söhne
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A fine German silver open faced keyless lever deck and pocket chronometer with power reserve indication, circa 1942. Frosted gilt 3/4 plate movement, 17 jewels, straight-line lever escapement with lateral banking extension on the entry pallet, mono-metallic balance with temperature adjustment screws, selfcompensating blued steel Breguet balance spring with patent stud fastening, swan neck micrometer regulator. Hinged silver cuvette. Brushed silvered dial with painted black Arabic numerals, outer minute track, large subsidiary seconds at 3, power reserve indication at 9 and original blued steel spade hands. Polished case, the back engraved with the watch number. Dial, case and cuvette signed, movement signed and numbered.
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Diameter: 60 mm
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Signed: A. Lange & Söhne Glashütte/SA
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This model of deck watch was made for the Kriegsmarine Observation Service. The caliber 48 was designed by Lange for the Wehrmacht and conceived to have a variation rate of less than 1 second per day. Its power reserve indicator was invented by Otto Lange and patented in Germany on Sept. 6, 1940, patent No. 732162. The Wehrmacht’s demand for these watches was so great that the Lange factory sent the watches to outside watchmakers for finishing. Along with many other makers, Lange engraved the movement number twice on the movement of those watches that were destined for Observatory trial.