Half quarter repeater with interchangeable cases Circa 1733

Half quarter repeating cylinder watch by William Threlkeld
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An English 18 Carat gold and enamel pair cased half quarter repeating pocket watch with original interchangeable case, Hallmarked London 1733. One of the earliest known English high quality cylinder movements, diamond endstone, repeating the hours, quarters and half quarters on bell. White enamel dial with Roman hours and Arabic minutes, blued steel poker and beetle hands. Two interchangeable outer cases, one dark blue enamelled case with ‘Greek bordure’, a blue ribbon and the initials WW & JJ to the back, possibly a wedding present, spirally engine turned, inside covered with silk, which possibly also is an indication of a special occasion, the second gold and leather with golden nail decoration, again the initials W & J, 18 Carat gold inner case, pierced, cock with grotesque face. Cuvette and movement signed and numbered.
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Diameter: 50 mm
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Weight: 135 g
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Signed: Willm Threlkeld London 626
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What makes this watch unique is not only that it is equipped with two high quality interchangeable cases, but also that it is one of the earliest English cylinder watches, first used by George Graham in 1726.