300 given the info provided
The Western Field 12 gauge side by side shotgun, serial number 30415 is valued at $225 in excellent condition. In fair condition it is valued at $125.
Market or kiln gun
They are very inexpensive, however the price depends on the model. You can expect to pay around $250 for a new Cai in .410 gauge.
depends on the exact model and condition. A Fox Sterlingworth in good condition is about $500.
In business from 1903-1913. Value seldom exceeds 100 USD
There are many good weapons produced in Belgium, you may have to name the make and year to get a realistic answer.
The shotgun is worth $150-$250, depending on condition. If the case is in good shape, it could be worth nearly as much.
Without knowing who made it, the question can't be answered
what is the model 101.7 in 20 gauge worth