Looking at the IMSB nut it looks like a stock nut to me...meaning Porsche. With as much dirt and oil as you have I doubt a new bearing was installed. If it was done a long time ago and the bearing was ceramic it would have to be a LN bearing.
I do not think Jake ever offered a bearing with a nut like you have. He uses Torque nuts. You may want to asking him if he ever offered a nut option like the Porsche stock nut. If I had to bet I would guess the IMSB has never been changed and the clutch and fly wheel has never been off the car before. See attached
http://lnengineering.com/media/catalog/product/cache/1/small_image/504x504/9df78eab33525d08d6e5fb8d27136e95/1/0/106-08.4.JPG
Threaded Mode
