German half seconds beating deck chronometer Circa 1916

Open faced silver deck chronometer with centre seconds
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An extremely rare, almost as new Glashütte half seconds beating deck chronometer with centre seconds, delivered to the Imperial Hydrographical Institute in Pola in 1916. No more than 38 of these pocket chronometers with central seconds were ever produced by Lange & Söhne.
Silver case, tiered, engine turned, case design “Jürgens”, gold hinges. Matt silvered dial, radial Roman numerals, centre seconds, numbered, blued spade hands. 3/4 plate movement, frosted, gilt, Grossmann’s pivoted detent chronometer escapement with 2 screwed gold chatons, gold screw compensation balance, very fine florally hand engraved balance cock, index spring fine adjusting device, chatoned diamond endstone on balance.
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Diameter: 62 mm
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Weight: 186 g
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Signed: A. Lange & Söhne, Glashütte B/Dresden
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Pocket chronometers with barrel Pocket chronometers are considered to be the precursors to deck watches. Lange & Söhne originally produced pocket chronometers with going barrels for scientific purposes. Often set in wooden boxes, they were to be used as deck chronometers on ships. Following this style the watches were designed with 14,400 alternations per hour; as a result the second hand was able to jump every half second. The watches all have pivoted detent escapements, which were designed in two different styles: one version was the chronometer escapement according to Berthoud, the other the escapement according to Julius Grossmann, which had an additional safety lever to prevent the escapement wheel from going on once the balance had been taken out.