I believe the 648 in the above translates to the 48th week of 2006 which is early December.batch # is Q648A289
The earliest E6300 date code in the [H] OC database is week 24 which was mid June. CPU-z now reports these early processors as Revision B2, Conroe.
On the xtremesystems forum people are assuming that because this new E6300 has the same L2 revision as the E4300 Allendale that the new L2 E6300/E6400 are now also Allendale. They're probably right but until I read that on the Intel site I'm not 100% convinced.
The reason Intel created the original E6300/E6400 was so they could sell processors that had problems with the on board cache. You get a better yield if you can sell your defective processors by disabling half of the cache. Their yields may be high enough now that they don't need to do that anymore so they can save money by building all of the 2MB cache chips on the Allendale core.
That's all just wild guessing. All I really know is that whatever you get, overclock the hell out of it and you will end up with a speedy computer.