Your gun was made in 1968. Check the link below for a Blue Book value based on condition. A professional appraisal is always recommended.
The earlier the better. 1 is in the Browning Museum.
You will have to call Browning.
The suffix of M71 was assigned to the Browning model BAR(Browning semi-auto rifle) which was made in the year 1971 in Belgium for Browning.
1981
All Brownings have serial numbers.
You will need to supply the serial numbers to your shotguns to get the age of your browning shotguns correctly.
Comparison to known serial numbers.
This would be a Browning BAR semi-auto rifle
See the Browning Company site under the tab "services" for date a serial > number was manufactured. > > At "Blue Books Publications" site, go to firearms and at bottom of page are > sections for serial numbers and an appraisal for $20.00 up to $500.00 of > value (then 2% of the value. ) > > Also do search for "George Madis". He is author of "Browning Date of > Manufacture" and has an extensive bilo of pulblications on Browning and > firearms, including miltary weapons. >
50-500 usd
1975
Check Browning's web site. They have sn data.