As you all know, or will find out very soon if you sell consumer electronics Google now requires 2 unique identifiers for ELECTRONIC categories.
Google base blog: http://googlebase.blogspot.com/2007/06/new-attribute-requirements-mpn-up...

The problem is that Ubercart only allows for ONE unique identifier called 'Product SKU or Model' (you can see this in create new product page)

To overcome this severe limitation and lack of dynamic evolutionary flexibility of the Ubercart model as it stands, there are 2 possible solutions:
- submit a patch to ubercart core or use a comma seperated multi identifier entry system for the SKU/model field.

This module will use the later solution, this new version module will be posted soon .