I tried arranging them on our dark bench top, looking for reflections, which I got, but the shelf was not wide enough and the reflections were sort of amputated through the middle. I thought that looked weird. So I arranged them on the black glass cook top with a black card behind, and lit them from the left with a flash, off camera. Much better. Now we can eat them.
My friend in the US commented as follows, "This particular orange, if purchased from the USA, is referred to as a “Sumo” mandarin orange because the top knot resembles the top knot of hair on a Sumo wrestler. At least, that is what our grocer told me when I asked. I thought that made sense. He said it is a relatively new fruit here and did not hit the markets until about 2011. The original fruit came from Japan and were sold with the name “Dekopon”.
So there you go. They taste good too, quite sweet, not tart at all, as I thought they might be.