The value of a Symonds "Keeper Gun" 12 gauge hammer-gun is actually dependent on a number of things. Some of these things would be the age and condition of the gun.
ya mum
The value of a Victor Sarasqueta 12 gauge side by side shotgun can vary depending on its condition, age, and any unique features it may have. However, they are generally valued between $500 to $2000. It is recommended to have the shotgun appraised by a professional to get an accurate value.
100-700 usd
50-425 USd
Seldom exceed 300 USD
1,800-2,500
No way to answer without a detailed description and pictures.
12g-9 = 3
300-450 or so
100-1000 USD and up depending on specifics
50-500 usd
870 and 700