Region Codes:

WA		- Western Approaches
NA		- North Atlantic
CA		- Central Atlantic
SA		- South Atlantic
MS		- Mediterranean Sea
CS		- Caribbean Sea
IO		- Indic Ocean
NP		- North Pacific
CP		- Central Pacific
SP		- South Pacific (not visible in the map)
GM		- Gulf of Mexico
ES		- Aegean Sea
BB		- Bay of Biscay
CH 		- Channel Area
NS		- North Sea
BS		- Baltic Sea
BL		- Black Sea
UC		- US East Coast
SC		- South American Coast
AS		- Arctic Sea (not visible in the map)
NW		- Norwegian Sea
BA		- Barents Sea
CE		- Canada East Coast


Navy Codes:

RN		- Royal Navy
KG		- Kriegsmarine
UN 		- US Navy
FN		- French Navy
RU		- Russian Navy
IN		- Italian Navy
JN		- Japanese Navy
CN		- Canadian Navy
AN		- Australian Navy
NZ		- New Zealand Navy
NE		- Neutral Countries Navies
CV		- Civilian vessels (civilian freighters, cruise liners, etc...)