I found Solingen made knifes which are very similar to David's piece, sometimes they have the etched inscription "high life" on the blade:
https://texasknives.org/tang-stamps/...lingen-dagger/
https://www.worthpoint.com/worthoped...dagger-knife-+
Some others have the inscription "Henry Kaufmann & Sons", which was a producer in Solingen, too:
https://www.collectorsweekly.com/sto...-dagger-from-b
So I think it is still realistic, that David's knife was also made in Solingen.