FAA English Proficient
This is really only applicable if you fly for a foreign carrier. No one in the USA cares which is part of the problem, I believe. If you just use the level 4 equivalent you will have to take the test again after 3 years if you are flying for a foreign carrier. Take the test, get your level 6 with no expiration date and move on. Interestingly enough the first time I took it in China I only got level 5. Guess the proctors English/Chinglish was better than mine...