There seems to be some misconception here.
The D1 steppings are ONLY on the newer P4-C CPUs. These have the 800Mhz FSB and HT enabled.
That means Kenshin has a D1 stepping for sure.
However, the C1 steppings are on the older 533 Mhz FSB Northwoods. That means all the chips up to and including the 3.06 Ghz had the C1 steppings. These are all 533 chips NOT 800.
All the C models have a) D1 stepping b)800 MHZ FSB and c) HyperThreading (HT).
These are NOT on the chips with C1 steppings, except for the 3.06 GHZ model which has HT.