The backs of the handles on the forks and spoons are simply stamped:

This is the stamp on the knife blade of one pattern:

And this is the stamp on the knife blade of the other pattern:

I understand what the "90" and "45" mean, and I understand what "NICHT ROSTEND" means. I cannot seem to find what ABFN stands for. I hope it's the manufacturer of the flatware, not just the blades.