Yes in the left corner there is country code with EU-flag stars. D=Germany, GB=United Kingdom, FIN=Finland, S=Sweden, DK=Denmark, NL=The Netherlands, EST=Estonia, I=Italy, E=Spain, A=Austria, B=Belgium, PL= Poland, CZ=Tsheck rebulic etc, etc. European countries which are not members of EU usually have their own flag instead of EU flag on their plates with country code.
You could make in the USA those plates with EU flag and lettering USA.... it's almost as funny as those Armenian EU plates that company sells....
On German plates the first letter/letters identify from where car is. For example M means Munich area, H=Hamburg, K=Cologne, B=Berlin etc. The bigger place ,less letters. Very small places have three letters, for example BGL means Berchtesgaden, FFB= Fürstenfeldbruck etc.
In Austria W=Wien, S=Saltzburg, G=Gratz. Smaller places have more letters, just like in Germany. For example Söll in Tirol have SÖL.
Most other EU countries does not have this kind of identification. For example we have it here in Finland back in 1973. For example Helsinki area cars had letter A & B. Uusimaa had U and forexample up north in lappland they had letter L. But we do not use that anylonger. Cars get letters in random basis.
Also what come to registration of cars in certain EU countries. In Germany car got new plates every time it got a new owner. In Finland cars have same plates even if it has been sold to some other person. In Belgium they had very interesting system. When you started to drive a car you got personal plates. When you bought a new car, you changed these personal plates to your new vechile. It was funny to see these plates when they were older, lots of bored holes, because you just needed to have new holes when you moved the plates. I suppose they do not use this system anylonger.
In UK the first letter of the plates identify the year model of your car. I suppose they are the only EU-country which use this kind of system.
So you can see most EU countries have their own specialities. Plate size is different, used letter fonts varies etc. etc. So there is NOT such a thing called EU-plates. Only that EU flag with country identification letters is the same kind in every EU country