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. Near mint guns and original box will command an extra premium. Recommend taking it to a gun shop for appraisal.
375-550 dollars, depending on overall condition of your shotgun.
It was made in 1970
50-600 USD or so
100-500 USD
50-575 usd
50-300 USD or so
Check the link for the Blue Book quote
Need more info / what is the serial number
50-1000 usd
Your Browning auto-5 shotgun should have the serial number prefix of 8V.This would indicate that your Browning was a Magnum model auto-5 because of the 3in.chamber.This was a new model which was first made in the year 1958 and seeing that your shotgun has a vent rib barrel;then the value will be between 450-750 dollars for a shotgun showing between 60%-90% of it,s original finish and a good bore.
Between 550-650 dollars in the condition that you describe.
B-80