This mark has come up here before (you can search for the old threads). As far as I know it has not been reliably identified. This is often the case with these French movements - sometimes the mark is that of the finisseur, but not always.
Later: Just did a quick search and found a Mougin movement which also had the Ch. Vcne. stamp. Looks as if that might be the finisseur or possibly a wholesaler since it is thought that Mougin bought in at least some of the movements stamped with his name.