Ian , thank you so much for the very kind words!
and Mark I appreciate as always your support.
I still believe this to be a Philippine item because of the rather vestigial form of the hilt, extremely light and seemingly a form reminiscent of the early hilts of espada ancha form. I agree that the Mexican influence was likely borne via the steady commerce between there and the Spanish possessions in the Philippines, and this is most likely a Spanish American war souvenier. The true espada ancha (=wide sword) in Mexico had devolved into virtually a large hunting knife or Bowie lookalike by the 1840's, and the blades were still heavy and typically undecorated, mostly blacksmith grade with crude presence.
Even though the term 'republic' is associated with Mexico with latter pre-revolucion time period and the 'rurales' para-military forces of late 19th century, in this application it seems more likely Philippine insurrection form.
Still a very interesting form, I have one similar but much more plain with a 'bolo' type blade.
All the best,
Jim