If you take the pads out you will eliminate the guess work and know for sure, looks easy enough.
Thanks for posting the pic Clemens.
Unfortunately the mechanism that allows the calliper to slide back and forth as the brakes are applied and released is not obvious from the angle you took the pic from.
Sorry ... the picture is from yesterday. Wheel is back on and car again in another garage.
For me, that was clearly a one piston brake. Since I had the last ten years only with motorcycles to do I can also be wrong.
