A French site lists a "MONTILIER - MONTILIER Watch Co (Domon Fils&Cie) Fabrique d’Horlogerie Montilier" watch; no picture given. Domon "Fils & Cie" translates to Domon "Wire & Co."; "Fabrique d’Horlogerie Montilier" roughly means "Manufacture Montilier Clock industry".
Though it looks (to me) like "Domon & CP", it may be "Domon & CD"... referring to his partner, Constantin Dinichert (worked with Domon from 1860-1916) :