Hi Tim,
I'm not inclined to place too much significance on the peg at this time.  Those other weapons you show are of recent manufacture, and typical of the type.  Your ivory-handled sword is much older, and much finer.   It is, frankly, a special sword.  
I'm certainly not suggesting the peg has no significance at all, but it fades into the background for me at this point when considering the other characteristics.
Andrew