Looks to be a combination of the handle of a US factory made combat knife, a random blade, and a hand made guard. Very cool primitive and dangerous look. Only a total badass would wield this dagger. I bought a box full of good old antique and vintage knives.
Most 19th century through WWII era. I assume this knife is from the latter or possibly even a bit later. Great looking piece for any collection! Possibly made by a deployed GI somewhere and brought home.