Extremely rare Swiss watch with mother-of-pearl dial Circa 1927

Gold open faced pocket dress watch by Patek Philippe & Cie.
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An extremely rare Geneva dress watch with mother-of-pearl dial, delivered to El Trust Joyero Relojero jewellers in Buenos Aires, circa 1927.
Signed, frosted, gilt bridge movement with wolf teeth winding wheels, Geneva quality hallmark, gold screw compensation balance, index spring fine adjusting device, and counterpoised Moustache lever. 18 Carat gold, polished case. Signed, mother-of-pearl dial with applied Arabic gold numerals, auxiliary seconds, and gold Breguet hands. Dials made from mother-of-pearl are extremely rare.
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Diameter: 46 mm
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Weight: 56 g
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Signed: Patek Philippe & Cie. Genève
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A nearly identical watch with such a dial is held by the Beyer watch museum in Zurich; it carries the movement number 189950 and the case number 285582 and was sold to the company Becker, Studer & Cie on November 26, 1920.
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Mother-of-pearl
Natural mother-of-pearl is the iridescent surface of the inside of certain shells. It is used as watch dials giving big stainless steel watches a rich appearance. Synthetic mother-of-pearl is made from fish scales and horn. Mother-of-pearl has opalescent shades.