I don't know what EP stands for - the initials, I mean. However, I believe it means that it was originally sold in the Post Exchange (PX) to a US Serviceman or Servicewoman serving overseas - often in Japan, Germany, Vietnam, or Korea.
It does not signify higher quality - but it does signify a distinguished and honorable past (my opinion).
It may also mean (no promises, but a good guess) that it spent most of its life being protected and treasured as a prized possession, and not being kicked to death as a working tool in the hands of a photo professional. I suppose you could say in that way it might signify higher quality - but I would not count on that automatically.
Your question is far from stupid - it's a good one, and one a new person to rangefinder photography would not likely know the answer to. Great question - and welcome to RFF. Hope you like it here!
Best Regards,
Bill Mattocks