English deck watch with stoppable center seconds Circa 1906

Half hunting gold cased pocket watch by Fattorini & Sons
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Rare very heavy English deck watch, Observatory Chronometer, with stoppable center seconds, circa 1906.
18 carat gold case with monogram, enameled Roman numerals and case punch Fattorini & Sons; lever escapement, screwed gold chatons and main plate signed “Fattorini & Sons Bradford Maker to the Admiralty“; original signed white enamel dial with Roman numerals, stoppable center seconds, gold second hand, blued steel hour and minute hands and small chip in center.
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Diameter: 53 mm
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Weight: 138 g
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Signed:  Fattorini & Sons Bradford, Tested at Kew the Observatory
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In the world of mechanical timepieces, accuracy is paramount. In the times before electronics, mechanical timepieces called marine chronometers were developed to a very high degree of accuracy for use in maritime navigation. To test the accuracy of such marine chronometers, watchmakers looked to a phalanx of astronomical observatories located in Western Europe to conduct assessments of timepieces. The observatory staff, applying a slate of accuracy tests, would either reject a timepiece as inaccurate, or, if it passed the stringent testing, would certify it as an observatory chronometer. Thus the “observatory trial” was developed as the standard process for determining accuracy of timepiece movements.