Since I'm in the States, I don't have the Euro version.
However, looking at my gimmick, I'd bet that it's the 'standard' 1 Euro coin (23mm) used because of size and popularity.
As for my thoughts, I could also see them using a 20 euro cent (22mm) or even the 50 euro cent (24mm) for a cheaper coin gimmick.
I was chatting with PM earlier and they didn't know which specific Euro was used either. They did assume it would be the 1 Euro also.
Best wishes...