Your gun is a mid production A-5 standard weight. They were manufactured by FN in Belgium between 1952 and 1976. It was offered in 12, 20 and 16 gauge with 26" through 32" barrel lengths.The finish is blued with checkered walnut stocks and a black buttplate that was marked Browning Automatic with FN in a center oval.U.S. production stopped at serial number 346,000. I checked the Browning website, Blue Book and a couple of web sites that I use. I believe Brownings US headquarters was in St Louis and they were imported into St Louis during this time.
Values are: Plain Barrel, excellent-$600, very good-$475, good-$400, fair-$250, poor-$175,
Matte Rib, excellent-$725, very good-$500, good-$400, fair-$275, poor-$200.
Vent Rib, excellent-$800, very good-$600, good-$450, fair-$300, poor-$250
Add 25% for guns with round knob pistol grip and 35% for straight grip stock. Add 20% for 20 gauge guns and 40% for 16 and 20 gauge guns that are new in box.
I hope this helps you,