Germany had the entire D block until 1947, when they were left with DA-DR. DS-DT are assigned to South Korea, and DU-DZ belong to the Philippines.Ture, but I was just thinking that Spanish speaking countries might have wanted to avoid using K and W as they were not "part of the proper Spanish alphabet."
Also true, but I guess N was already taken.
Note that Germany has the "D" series (Deutschland).