I have an old 20 Gauge Shotgun I need help Identifying. Its marked ROBUST #222 on bottom, Right side is Marked MANUFRANCE-SAINT-ETIENNE, Left Side is marked FUSIL ROBUST BREVETE S G D G. Any Ideas on what this is? Its missing all of the stock and I would like to replace and make a Wall Hanger out of this. Will any other models fit this gun. Appreciate any help anybody can give.