These unsharpened kaskara have always seemed a bit of a mystery to me.
I'm unfamiliar with the idea of cast blades for kaskara. Could you elaborate a bit more on that?
I used to own a croc kaskara (image attached) that was also pretty dull without a proper edge.
However not all the thuluth covered blades are like this - here's a link to one a forum member was kind enough to allow me to display on my takouba website -
http://takouba.org/takouba41/ - it features a Solingen blade.