Valenciennes is the region in France where it was made. "Morin" may well be the maker, although I do not have a reference on that maker specifically. There were many French guilds producing arms in the mid-1800's (1860's time frame when pinfire was popular). Value is going to depend on the overall quality, amount of decoration and condition - could be anywhere from a couple of hundred to well over a thousand.
Could be a serial number, assembly number, or year
With the serial number that you provided,your Ithaca double barrel shotgun with the damascus barrels was produced in the year 1900.
A Damascus twist steel double barrel shotgun is an antique shotgun made by layering iron and steel and welding them together. This kind of shotgun is worth approximately $3,000 depending on the condition of the weapon.
NO! This is EXTREMELY dangerous!
That is impossible to determine without knowing the manufacturer and model of the shotgun.
no not all twist barrells
You may have some success at the shotgun world website, (shotgunworld.com) there is a vast network of collectors and shotgun experts there that may be able to help
Follow manufacturer's instructions.