P.E.F. Last Directive Signals and Camos that give you extra Credits in Battle. ( Normaly 20%, a few 30%)
(As I do not have accsess to my Account I can not tell you what is available from the Arsenal for Coal.)
Zulu (this signal can be bought from premium shop in bundle form)
Type 20. Perminant.
Gamescon = 50 Doubloons.
Revolutionary = 60 Doubloons.
Ocean Soul, FTW, Full Moon, Hunter, Blue Lagoon, For Meritorous, Adler, Cleveland Freedom, all are Not For Sale.
KII & Roma Kobyashi Camo from Premium shop.
Adler, Fly Fire, Galaxy, Auroru, Norma, All-destroyer, Paris Hall Carrier, all repeatable in game for 8000 Doubloons.
Info from = http://wiki.wargaming.net/en/Ship:Camouflage
Hope this helps
ZULU signals in your Arsenal, cost = 6400 coal, less your 25% coupon.
Ocean Soul & Revolutionary Camo's also in Arsenal, cost = 16000 Coal, less your 25% coupon.