It's got a NATO designation and a year, but English as a Second Language is a new one. I'll have to keep looking around, but just for a SWAG, I'd say Greek maybe...maybe some small euro country. Greek has a few 3 letter headstamps that start with an E.
I've got some 5.56 brass with that Circle +. Think I found it at one time but have to get some confirmation.
I'm thinking its Greek but don't quote me.
It's somewhere inside 5 gallon buckets of that caliber brass so I'm not going to go searching for some.