I seem to remember wavy bladed daggers from small ads in the back pages of Argosy and other similar magazines of the fifties. I think the hilts were spiral with a ball and claw pommel.
I not only remember the daggers you are talking about, but somewhere around here I still have one that I paid the grand total of $1.50 for in the late fifties.
Most of these were of German manufacture (like the one I still have) but I believe some were of Japanese origin as well. I can with confidence say that the blade of this piece definitely does not come from one of those daggers.
P.S. I meant to add that if you look at the first two photos of the complete dagger above you will see one where the blade was just cleaned and one where it has received a vinegar etch. In the lower photos of the blade only you can clearly see the inserted hardened steel edge.