Scot Reader gave what's probably the best available estimate in "inside T206"
http://www.oldcardboard.com/t/t206/i...al-edition.pdf
Best to read the whole thing, so you can be as confused as the rest of us.
Seriously, it's the best explanation of things so far. There are things I might not agree with 100%, but they're more of a fine detail thing, and would make it maybe 3x as long. As it is it's an excellent explanation, and just right for someone who's really interested but not crazy.
Steve B