I responed to this question on another forum. Here's what I posted:
I believe your house mark is a French mark used on exports since 1884
http://www.cgo.com/or/objets/poincons.htm
See the scans below for Christofle and Roussel Fils et Cie examples.
Not sure who used your mark. Possibly Ernest Prudhomme.
viewtopic.php?t=6299
The symbol in both your mark and Pruhomme's is a caducée ( caduceus in English ).
I enhanced your picture of the mark.
Ernest Prudhomme used an EP mark, with a caducée inbetween ) from 1891 to 1928.
I'm guessing your mark would be a later mark.