I'm a novice here, but I just wanted to say that your sword is magnificent! I love this style of guard. I would wager the second opinion as well, but perhaps early 17th century, Dutch colonial, perhaps made in Indonesia or Shri Lanka (colonial lions similar to those VOC swords of the period?). I see why it could be 1660's, as the shell is curved vs. flat outcropping seen on early hangers. Also, the timeline would fit with the early Anglo-Dutch Wars, when similar pieces were being produced-