I thought about its being a plug bayonet, but all the ones I've seen had a bulge in the handle, then a tapering, then the hilt and dagger. The similarity in the look has to do with the way the blade tapers, but the position of the hilt is wrong. See the picture
here. I'm thinking both the plug bayonet and my dagger were probably based on the blade design of some polearm, and that's why they look similar?
