The following link will aid you with the manufacture date of your Browning firearm. Browning has their serial number list wrong for 1975 and earlier firearms. They have the sequence backwards. Review this article for the correct sequence on those years. http://www.pumprifle.org/index.php/member-articles/36-browningblr
This link provides a historical timeline for various Browning firearms.
The Browning centerfire Pump Rifle (BPR) was built from 1997 through 2001. The Pump Rifle BLR link above above also has some useful information on the BPR and the Dualis.