I don't know what it was, but it was odd. He was in to it, whatever it was. She is an Ovation artist, so I'm thinking that uke was custom for her. It looks just like the custom Adamas that they released, all black with the bubbly sound holes.
For those who aren't aware of Kaki King, she is a brilliant guitarist. She's a Jake on the acoustic guitar. I kind of like her rocking stuff, though her earlier albums that are instrumental are also awesome. If you can find it, you must get the vinyl EP she did with the Mountain Goats called "Black Pear Tree." It is outstanding.
Cheers.