As Alice has said, it would be helpful to show us more photos to try to be accurate in dating or assessing the style.
From what I can see, it appears to be an early 20th century man's frock coat. Looks Edwardian era. If you can lay it out so we can see the shape that would be helpful, especially the waist line area and the back. To me it does not look like a top coat, but looks more like a frock coat. A frock coat would not be worn over another coat but worn by itself.
It may be a fraternal frock coat, worn by a member of some organization. But it may just be a simple black frock coat with no ties to any group.