As with any firearm, it is not possible to accurately appraise a gun without seeing it. Condition, and original configuration will determine value. Other factors such as rarity of caliber or guage and higher grades have significant impact on value. Recommend that you see a local gun dealer for an appraisal. You can also do your own investigation by looking at other models being sold that are in the same condition as yours. Try the gunbroker.com or a periodical called "The Gun List" You can also reference the Blue Book of Gun Values which can be purchased on line at various retailers.
In 90%+ condition about $700 for a 20 gauge and about $550-$600 for a 12 gauge.
Without more specific information on the fininsh and condition; 100-1000 USD
50-1000 usd
Made in 1979. Without more of a description, the value range is 500-1000
Alan Browning died on 1979-09-07.
You MUST call Browning to get a correct answer.
1979
Unless it's proof or a very high grade coin it's just a dollar
50-400 usd
You have a 20 gauge 3" Hunting model manufactured in 1979. Depending upon condition $600-$1,200.
This is a mixed question. Which gun do you have? An Auto-5 Light twelve, is not a pump shotgun, it is a semi-automatic. Since 1979 is before the Browning Pump Model BPS was introduced, It is assumed you do have an A5. Value depends on condition. Typically with average use, these guns sell in the range of $500-$750 depending on condition. Mint in the box will go $1000+, but remember that this model has a fixed choke in 1979 and won't bring as much as the later Janaese made Auto-5's. The nickel plating you mention is not Browning factory finished. Browning never plated an auto5. You could have a silver receiver that was custom engraved, but it wouldn't be plated. If someone actually did nickel plate the gun, it could decrease value.
1979