Fine German silver lever watch with power reserve Circa 1942

Silver open faced keyless lever by A. Lange & Söhne
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A fine German silver open faced keyless lever deck and pocket chronometer destined for observatory trial with power reserve indication and special Guillaume type balance, circa 1942. Frosted gilt 3/4 plate with separate bridge for the escape wheel, engraved twice with the movement number, 17 jewels, straight-line lever escapement with lateral banking extension on the entry pallet, Guillaume type balance modified by Lange, blued steel Breguet balance spring with patent stud fastening, swan neck micrometer adjustment to the regulator. Hinged silver steel 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 issue number. Case and cuvette signed, movement sigend and numbered.
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Diameter: 60 mm
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Signed: A. Lange & Söhne, Glashütte i/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.