What does plaque or g 20 microns mean on watch case?

"Plaque" on a watch case typically refers to a layer of gold or another precious metal that has been applied to the surface through a process like electroplating. The "g" likely stands for grams, indicating the weight of the gold used in the plating process. The measurement of "20 microns" refers to the thickness of the gold layer, with one micron equaling one-millionth of a meter. This measurement indicates the quality and durability of the gold plating on the watch case.