Pictures could be better for trying to lock in on this knife, but from what I can see, the sheath looks like one of the variety of known WW2 era type. Examples of the 1219C2 pattern knife with only the name KA-BAR and no branch of service are a known variety. They aren't the most common. Unfortunately I don't know of anyway to say for certain when it was re-handled. Sometimes the material used can provide clues but not always. Too bad, there's probably a story behind this one, but don't think anyone is talking.