Interesting. The progression of "A", "B", "C", "D", "E", "F" corresponding to 11.1, 11.2, 11.3, 11.4, 11.5 is hard to ignore. Of course, it's apparently not always going to match up that well. I noticed that the Build Version for my copy of Lion 10.7.5 is 11G64. Apparently some "point updates"...