The pictures don't enlarge but it looks to me as if it has both a bayonet lug and provision for a sling which makes it very likely an officers' musket rather than a fowler. I'd place it in the middle of the 18th century. At that time, the fuzee was a regulation arm for French officers and at least some of them were supplied by the government. This doesn't look as if it conforms to the issue pattern but it is unlikely that all of them, especially private purchase arms, did.
What we now call Belgium was under the rule of Austria, as the Austrian Netherlands, between 1714 and 1797 which must cover the period of use for this gun. I've no idea what if fuzees were commonly used in the Austrian army at the time but I have owned at least one clearly germanic example from the same period.
As to the stock... how do you know it is maple? Could it be another wood with a similar grain structure? I have seen striped ash stocks and ash was a commonly available wood in Europe. Also, at a later date we know that maple for gunstocks was imported to Europe... whether it was done this early has yet to be proven but in the mid-18th century America was the main source of hardwoods for the British - and perhaps other European markets.
