No idea. Doesn't it have any inscription anywhere? The blade? The pommel? It's unusual for someone to make a sword or knife and not leave a 'maker's mark'. Have you had the blade X-rayed?

I don't think it is a Calvary saber as someone else suggested. A saber usually has swept or curved blade to use from horseback. The strait blade makes me think it was designed for someone to use on foot.

Could it be a ceremonial sword, such as Officers are awarded? This sword is kind of plain looking for that, also a ceremonial sword wouldn't normally be used in fighting, and wouldn't have the leather thong.

With the spear point tip and the S-shaped guard, it almost looks like a giant bayonet. Also, I don't see a blood gutter.