Dear Ed:
On page xii-5
(of the Geneal.Guide to East and West Prussia)
you translate
Frisches Haff - Fresh Lagoon.
While this may be the popular conception, I suggest that this
was not the original meaning.
I recall having seen a copy of an old map where this lagoon
was called "Frisisches Haff" (Frisian Lagoon), presumably because
Frisian immigrants had been in the area since the Middle Ages.
This should be pointed out in a later edition.