Pretty well known here though especially as Guernsey was also occupied too (The Channel Islands as we call them).
And to many stamp, coin and banknote collectors. In the same way that the US currency marked for Hawaiian and North African use isn't a well known fact either over here though, I suppose. If I hadn't been a banknote collector I wouldn't have known about the brown or yellow seal notes.
It seems that the $2 note was used more in Israel (with the vast majority being shipped over there) than in the US which I thought was weird but it was in everyday use there even in the 1990s whereas I'd heard that not that many Americans even knew about them.