Pierre Le Roy , the eldest son of Julien Le Roy, as important or more important as his father, was the professor of Ferdinand Berthou, who will later become his fiercest competitor. He created the "precision theory" which made it possible to remarkably surpass the H-4 of Harrison, in 1760 he applied the "stackfreed" or brake regressive, the balance For temperature change and isochrone spiral , among other discoveries. For years, he continued to sign the watches of his workshop under the name of Julien Le Roy in homage to his father. He was the watchmaker of Louis XVI's room.
Illustration: Gousset watch In silver with box smooth for The Turkish market signed Julien Le Roy in Paris, and produced by his son Pierre. The dial has a central enamel in or which attracts attention, with the signature of the prestigious watch clearly visible. This type of watch, like the watches with several Prior boxes, and those whose enamels are spectacular and striking, have been ordered in Swiss by Turkish clocks.