Welcome. Hope you stop by on a regular basis.

The gun does not have any Nitro proof marks that I can see. It is not safe with today's normal ammunition and requires low pressure loads.
It "appears" to be in good condition, but is not very collectible.

For more on Janssen Sons & Company:
http://www.littlegun.be/arme%20belge/art...%20cie%20gb.htm

http://damascus-barrels.com/Belgian_All_Proofmarks.html

Pete