That sn does not follow Browning's convention. Call Browning.
What is the age of your browning 325 grade 6 serial number 16179NM?
The 2 letters in your serial number(NR) indicate that your Browning 325 grade VI was made in the year 1997.
You will have to call Browning to find out.
The 2 letters NZ at the end of your serial number indicates that your Browning 325 shotgun was made in the year 1991.
Your question cannot be answered without you providing the full serial number to your browning.
See the Browning website- customer service. Date of prodcution by serial number listing.
1988
1994
1992
The last 2 letters in your serial number NZ indicate that your Browning 325 in 20 gauge was made for browning in the year 1991.
You have not listed the entire sn. You will have to call Browning to find out.
A citori 325