Wouldn't this be an example made by African locals inspired in navigator swords, which prevailed through centuries to be used for ceremonies or prestige, the so called MBELE A LULENDO (sword of power) ?. In this specific specimen, the date 1697 could have also been borrowed from early original examples. This one could be as late as from the 19th. century. The variation in model details may as well be 'authors imagination'. Although these swords may be acquired in (Nothern) Angola, it is obvious to expect that their design found its way there descending from neighbour Southwest Congo, where its influence was provided by navigators is registered.
But of course, anyone with knowledge may certainly correct me ... partly or totally