St Etienne is a city in France where many firearms manufacturers have been located for about as long as guns have been made. Cannoniere means "gunner". Sanner appears to be a family surname, so, the gun was made by (or for) Mr Sanner in St Etienne. If you can describe the gun more completely (muzzle loading, or if breech loading, pinfire or center fire? Back hammers, side hammers, or hammerless? Side lock, back lock, box lock? Damascus, twist, or fluid steel barrels?) we may be able to guess a bit closer to the guns age. Also, if the barrels can be removed, look below them and on the bottom of them for proof marks and tell us EVERYTHING that is written or marked on the gun. And if you want an estimate of the value, you will need to give us a good idea of it's condition - is it closer to a rusted hunk or to a factory new gun?
Fusil Robust is a model, not a brand. Made in St Etienne France by ManuFrance, in business since the 1910's. Not true.
Obviously French, but not much else. The proofmarks under the barrel and type of action will help date the shotgun.
That is impossible to determine without knowing the manufacturer and model of the shotgun.
Without a detailed description, it could range from 10-10000 USD
mossberg
Not nearly enough information to make a guess. Need to know the exact manufacturer and model number as well as the condition of the shotgun.
In America, we contact the manufacturer directly. They are often willing to share information regarding their products gratis.
Follow manufacturer's instructions.
You also need to know the manufacturer and model. Then look in the Blue Book of Gun values to find out if this gun is listed. If not, you may be able to get information directly from the manufacturer if they are still in business.
@ turn of the century
Savage
Between 1894 and 1930.