Form what I can remember, the 920 had C0 at launch time and then moved onto D0 and I believe the 930 was all D0, I am not sure about the 965, as I have never really looked into that chip much. Intel as far as I know doesn't make this info available on their sit and if they do its probably a pain to find like a lot of things there
I will try to find a database or chart with this info on it. I'll post it up if I do.
Copied from HardwareZone.com ("A quick way to distinguish between the two Core i7 steppings is to check if the small vertical marking (highlighted in red) is present. CPUs with the new D0 stepping do not have this marking. So in this case, the chip on the left is the new Core i7-975 Extreme Edition.")