Interesting gun: it has the appearance of a bucaneer type of 1700s French musket. It has a rounded lock place and hammer however which would be unusual if French. Condition is unusually fine, however.
Here is my take on it; likely origin is a Stoeger Arms, or Bannerman Arms, 'African' trade gun. If it is such, it is a well made piece, better than most, and it has a lot of appeal. Would make a good shooter, too.
I wish the seller had given better photos and more detail in the description to allow more analysis.
Best-Dick