The E-series CPU's are core-series CPU's.
For example, just looking at my price list, we have the following E-series CPU's:
1. E4500, which is a Core2Duo 2.2Ghz with 2MB of cache and an 800Mhz FSB. This is an Allendale core CPU. It does not list as a Pentium anything, it shows up as a Core2Duo.
2. E4600, same as above, but 2.4Ghz
3. E4700, same as above, but 2.6Ghz
Now the 2-series, IE the E2200 and the 2180 are also Allendale, but are marked as Pentium D-Core, so if those are the ones you are talking about, the E2xxx CPU's, then I apologize, as their nomenclature does seem to be different, even though they are the same core.
When I read your post I thought you were talking about the Pentium-D, like the 925 for example, which is simply a dual-core P4. If I misinterpreted what you said, then I apologize.