If serial number data has been published you can look it up.
To find out how old a Winchester rifle is one would need to take the rifle to an appraiser or gun shop. The gun shop will be able to look up the gun by the serial number.
We MAY be able to find answer for you, if you can find the MAKE of the rifle for us.
Which model??
Old gun catalogs
Library, old gun publications, internet.
You will have to contact Remington to find out.
This rifle was made from 1971-1988.In order to find the year of manufacture you would need to post the serial number.
Find a professional appraiser.
You will have to contact FN to find out.
Go to proofhouse .com with Colt serial number to find the date of manufacture.
You will need to include the model number to your question to find a answer.
Library and old gun publications