U2713h vs u2713hb

Hi,

I ordered an U2713h to Dell the last week, and today I received an U2713hb (made in China the November 2012, Rev A01 ).
Does somebody know what mean the "b" after the model name (U2713h) , it's like a new revision?
I will try this monitor this WE, hoping that is a revision without problems like USB3 or density and color shifts reads in some forum and dell forum (http://en.community.dell.com/support-forums/peripherals/f/3529/t/19489601.aspx)

Thanks
Salvo