That's an interesting thought RD. Case hardening typically produces a very thin surface treatment. It's a cheap way to improve a lesser quality steel that you do not expect to wear much. The amount of good steel needed for a razor, and it's ready availability in Europe, speaks against this possibility. But it's still possible.
Another test of time would occur during honing. At the edge, the thin case hardening would be abraded away exposing the softer parent material. If this blade resists surface abrasion but is difficult to hone, you might be right.
FWIW, I like the look of it.