East Germany used the series ET--
I remember the code that was used up to the middle fifties
UK = GA--
Heathrow was GALA Southend GAHC Jersey GAJY
Holland PA-- Amsterdam PAAM Rotterdam PARD
Belgium ON-- Brussels ONBR Ostend ONOS
France FF-- Calais was FFMK Le Touquet FFLT
worked at EGMC then and these were the most commonly used for Channel airways and Channel Air Bridge flight plans
I cant remember many others, anybody else remember???
WB