Value is too difficult to be accurate without seeing the gun. Condition which includes the amount of original finish and original configuration will determine value. Auto 5's with poly-chokes, compensators and recoil pads (other than Mag 12's) will reduce value. A rough ball park figure would be $250-$600 range for this gun. Near mint guns and original box will command an extra premium. Recommend taking it to a gun shop for appraisal.
Thats a a5 magnum twenty made around 1970 value 1400 in mint condition
75-575 usd
100-600 usd
50-500 usd
50-550 usd
50-500 usd
Between 6 and 7 hundred dollars.
Basically impossible to value with just the serial number.
You will have to call Browning with the sn to find out.
A billion dollars
100-1000 depending on specifics
50-500 usd