Hi Mark,
personally I still feel that this sword could be African ....don't forget that the Spanish had colonised parts of coastal Western Africa, as did the Portugese. The length of blade does suggest naval useage...perhaps a direct copy of those seen carried by the ships crews and onboard Marines. As the Spanish were involved in the Slave trade ....there is the possibility that this sword, or perhaps an earlier version, was issued to a native whom 'helped' in this activity, and would be a status symbol to show the individual's rank
I must point out that you could be totally correct, but without provenance and the age of the sword being unknown, this sword will be impossible to ID. I have several weapons that fall into this 'unknown' catergory .....the 'Mystery pile'
All the best
David