Really an interesting sword! Not much to add over what the others have already said. Definitely French, not only for the blade, but for the lion pommel (seen on certain types of french swords) and spiral quillons. As I've never seen this pattern before, wondering if it's custom made for an officer? However, I don't underestimate the multiple divisions of troops and their accutrements. Used to have a cuirass of French origin that wasn't identified for over a decade despite the sunburst badge to the front (ended up being a M1863 Carabinier's-
). Point being, perhaps a rarer pattern for a special unit?
mark