Seamaster De Ville Case Manufacturer

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Hello everyone,

Does anyone know the case manufacturer that matches this symbol?



I was aware that companies like Ross, Dennison, and Centrale Boites all manufactured cases for De Villes, but I haven't heard the name of the company whose hallmark is the triangle with a circle on top.
 
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That is the mark for Ervin Piquerez S.A., Bassecourt, Switzerland.