Barnes & Noble's nook looks to be going through a further hardware tweaking, with a new version of the 3G/WiFi ereader showing up in the FCC database. The nook BNRZ100-01 - codenamed "CR Nook/Bravo Delta" - looks to be a minor revision of the original model (the BNRZ100), swapping out the 3G modem used for an updated version.
That updated 3G card is the Sierra Wireless MC8201V (again, locked into data-only mode), supporting the 850 and 1900 bands. That means that the triband UMTS/HSPA (which added in 2100MHz support) capabilities of the original nook have been lost; it's possible this is a cost saving measure on B&N's part. Of course there's also WiFi b/g for local networks.
The confidentiality letter B&N submitted to the FCC requests 180 days secrecy on the external and internal photos, together with the user manual for the new nook model, from the date of approval. That's the maximum period of confidentiality a company can request, and probably doesn't give us a hint as to when B&N plan to debut the new model.