Hi Clark,
I don't think wrist escutcheons or plates were associated with any style. They were a feature of the quality of the gun not some artificial type label. French makers of trade guns made a range of guns varying in quality. Higher end guns often had fancy cast and chiseled wrist escutcheons that look to be mounted like English fowlers at the time, with a screw through the wrist threaded into a boss on the back side of the plate. Cheaper guns might have simple sheet brass or silver plates that were pinned in place. Some guns had no wrist plates at all.
dave