I saw your post in another forum (watches).
The case has no British hallmarks whatsoever, and not even import marks for Birmingham.
LEB maker`s mark does not exist in Birmingham Assay Office.That said, the case is most likely German made,of lower silver standard than sterling (e.g.800 instead of 925 sterling) and therefore not legally qualified to be hallmarked in Britain.
Stolz engraved ‚‚Fine silver‚‚ to satisfy the customers.
You can embed the images here,it's interesting.