B-Stock probably means devices checked for function.
If the unit doesn't look like it has been thru combat it receives the hard reset and a wipe down.
I'm betting most of these were just returns, warranty swaps or corporate turn-ins and weren't mistreated.
My previous experience with B-Stock or refurbs has been good.
I've never been disappointed to date.
I thought some of you might find this helpful...

I mailed Expansys this morning asking if the RM-877 models were unlocked and I received the above reply very quickly.