Chinese or Philippines short saber?
 

I picked up this small (72 cm overall) saber from a Dutch seller, which I suspect is most likely from the Philippines (Luzon?), or possibly China, mainly based on the forward facing quillon, the substantial ferule, the very slight, barely noticeable bulge in the blade profile (starts at 35mm, then steps in to 34mm at the narrowest point, then out again to 36mm at the widest point), and the way the guard is attached. It has a wedge section blade that tapers gradually from 9mm at the hilt to 2mm at the tip.

However this is the first such saber I've seen with a P guard, and a fairly thick one at that. And most of the ones I've seen from Luzon have more of a forward curve to them whereas this one simply curves back (although it does lean forward a bit as the grip is angled ).

It is quite worn and has a deep dark patina, and I think it has been coated with something like varnish (as is often seen), but I can't really narrow it down much in time (I guess the default assumption would be late 19th/early 20th century) as there are no markings. The grip is split to the bone but it feels solid as it's helt together by the ferrule and the peen - though the tang is quite corroded as can be seen through the crack in the grip. There are some old nicks in the blade that hint at use (though in what capacity is of course impossible to say).

If anyone can narrow it down for me in time and/or place, it would be much appreciated.

Not in the best state, but this one cost me approximately three pizzas, so I took a small gamble. :D

Could it be a boarding sword?

Possibly. It's got some heft to it for the size. Not unlike a briquet or some naval cutlasses. Other than that your guess is as good as mine. The Chinese river pirate swords came to mind (also because of that quillon), but I've never handled one of those before.