Here are your pictures:




OK, from the proof marks, the gun was made between 1878-1897. That is the range for "Not for Ball", which basically means the gun has some choke. The Crown with AF is the Francotte maker's mark.
http://damascus-barrels.com/Belgian_All_Proofmarks.html
http://damascus-barrels.com/Belgian_Trade_Marks.html


From the serial number, according to this list:
http://www.doublegunshop.com/dgsnos2.htm

The gun was made in 1889.


Pete