James Trilling, "Ornament: A Modern Perspective" p253
The term "Damascus steel" refers to two quite different techniques. "Oriental" or "true" damascus displays a light-and-dark crystalline pattern on its surface, while in "mechanical" or "pattern-welded" damascus the pattern is formed by two separate alloys which turn different colors when etched. .... Of the two types, only pattern-welded damascus has a long if somewhat sporadic history in Western craft.
I think we can be sure this gun was made after 1898. In which case, the faux damascus laws would be in effect within Belgium.
None of the barrels shown above says, "Damascus" on them. This would be in keeping with the laws. So, is it possible we have a faux damascus? Steel barrels that have been say coated in wax and dipped in acid to produce an etched damascus-like pattern? I am just speculating. The only sure answer would be a metallurgical examination of the tubes. There seems to a some "depth" in the picture, as though some metal has been taken away.
Sweep, can you feel this "pattern" when you run your fingers over it?
Pete
