Thank you. Your hat discussion is fascinating. The only place you see Americans wearing bowler hats nowadays is riding horses, but I think they call them “riding derbys.”
Your dating of the photograph sounds about right.
Did you see Tarantino’s “Inglorious Basterds”? In it, a person posing as a Nazi is betrayed by using the wrong three fingers to indicate the number “three”. The German convention is supposedly different than the American one. I don’t know if the movie is accurate or not.