Walt, it's a casting flaw in the case at the J-tube. If you look at the outside of a case near the oil cooler, you'll see the equivalent. This just happens to be where most people don't look.
The Porsche bulletin was 8911 that covers the repair.
http://forums.pelicanparts.com/porsche-911-technical-forum/850925-911-sc-oil-leak-notch-above-oil-cooler-case.html