English triple-cased watch for the Ottoman market Circa 1800

Silver, horn verge clock watch by the firm of Markham, Marwick et Marko
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A very rare English, silver and under-painted horn, triple-cased clock watch of the early 19th century. It was made for the Ottoman market.
This antique timepiece boasts a stunning gilt-finished verge movement, with a chain fusée and a large three-armed balance. The champlevé dial features Ottoman numerals, outer five-minute divisions, and elegant poker and beetle hands. The watch comes with three cases, including a silver case covered in under-painted horn and two polished plain silver cases. The movement and dial are both signed.
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Diameter: 70 mm
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Signed: Markham, Marwick et Marko, London
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Marking:
[1] Crowned leopard’s head crowned (London assay office mark);
[2] Lion passant (English quality mark for sterling)
[3] K 1805
[4] W D (pricked, not stamped)
Location of marks: [1]–[4]: both silver cases hallmarked