At least in Scandinavia and Germany two notes are marked differently than in most other countries:
- B -> H
- B♭ -> B
I have heard that this is due to mistake in interpreting messy sheet notes, as ♭ is close to b and ♯ resembles H. The story goes that a musical scholar thought that the note is H and when B was later encountered, it was deduced that it must be a special name for H flat as H was already established in its place. But this may be an urban (or actually historical) legend.
How did this difference come to be?