He may have read the inspection stamp wrong or read the wrong number or Letter. Most of the outside hammer Belgium made shotguns where made prior to 1912 ) and have Damascus barrels. If it does have Damascus barrels then it was made for Black Powder. If does have Damascus barrels, then shoot it at your own risk, that is JMO and the opinion of a number of others. After WWII, around 1920 the Belgium's once again started exporting to the US, how ever by that time internal hammers and steel barrels was the standard. However there is no line in the sand it regards to the last black powder shotgun was made, just sometimes in the early 1900's every one was switching to smokeless powder and by the 1920 I would dare say there were none made.