One of the things that threw me was that in Japan they can't use the name Logitech. They use Logicool instead. the packaging looks the same. When I was shopping I kept looking for the Logitech models that I had read reviews on. I thought all the Logicool models were Chinese ripoffs of Logitech. A few web searches finally put me straight.
The Performance M950 was not cheap, but it's the most frequently used piece of hardware after my keyboard and I didn't want to skimp.
That said, I didn't see the Logitech Trackman Marble in the stores...just the Wireless Trackball M570 which is the thumb-ball unit.