These are Vespa Orientalis. According to the pics on Wikipedia. The diameter of the coin is 27.3 mm. So it's big. And scary. But (I now know) has a sting which is no more dangerous than a wasp (yellowjacket), and they are less aggressive than a wasp.
I caught this one taking a swim in our pool. I helped it on its way, I'm afraid, because I wanted to photograph it. The previous day I had seen one kidnapping a bee from its hive. So I felt its species had it coming.
In photo below is same specimen plus a regular wasp.
In photo below I tracked them down to a wall of a cemetery, behind which they were nesting.