You may find the info you seek if you go to Brownings web site and look for the customer service dept. then look for info on firearm history I believe and there should be a way to provide the info to look up the age of your Browning.If not please provide the serial number to your Shotgun to me and I will date your shotgun for you.
Check the receiver
In order to date your Browning 20 gauge shotgun you will need the prefix to the serial number it should look like a number followed by the letter Z.or 2 numbrs followed by the letter X.
Browning.com has sn tables you can look it up on.
Go to Browning.com and look for serial numbers under customer service
Depends upon what model 20 gauge it is. Look under the tang on breakdown type guns. On automatics is is on the receiver somewhere.
Look at the serial number again as this is imcomplete. Go to Browning's site, Support, Date your firearm and they have a list of dates.
Value of a shotgun is driven by several factors. Condition, model, area of the country it is sold. Look at one of the used gun sites like gunbroker.com. Then compare.
According to Browning's site, there has to be a lot more than those four digits in the serial number. Look carefully again, and re-post your question.
Look at the manufactured date link on the Remington Society of America for details.
You will either have to call Browning and give them the serial number, or you can look it up on their web site or Matt Eastman's book or the blue book of gun values
Look on the receiver and barrel.
Blue Book of Gun Values; Browning website under customer service