I'm with you Ian, and I can only imagine this was probably perceived as a 'sleeper' with the allusion to a Revolutionary War hilt. It seems like all manner of put together and contrived pieces end up in the 'catch all' of Filipino weapons brought back during military service from Spanish American War through WWII, as Katana has suggested.
While the spiral grooved grip and the animal head, with the prominant ferrule of the hilt suggest Revolutionary War period American hangers and sabres, the monkey head obviously deters that possibility. It does seem that a clever artisan created an interesting amalgam of features in this item.
The monkey head may somehow represent the monkey god of Hindu and Buddhist pantheons, but it seems strange how this image might apply to a sword/dagger fashioned in the style of early Spanish espada anchas with an American Revolution form hilt. Further, there must be some symbolism more aligned with Filipino tradition or folklore concerning the monkey head.
The agreed flimsy 'knuckleguard' hilt seems to correspond to vestigial representations of full guarded hilts often seen on Spanish colonial 'refabricated' items that are often found in the bring back category.
It is an interesting item, and clearly curiosity prevails as seen here
All the best,
Jim