Is Plaque OR G20M on the back of Cartier watch mean 20 microns gold over silver?

Yes, "Plaque OR" on a Cartier watch indicates that the watch is gold-plated, while "G20M" signifies that the gold layer is 20 microns thick. This means that the watch has a layer of gold over a base metal, likely silver, providing a luxurious appearance. The gold plating is intended to give the watch a high-quality look while being more affordable than solid gold.