Part numbers

I have a My Book essential  that has quit working.  The Hard drive itself seem to be working.  I can feel the drive spinning inside and in addition when i connect it to another computer like an internal drive the computer will detect the size of the drive.  So i am thinking the control board has went bad.  So i decide to find an identical model and try using that control board to access the data on the drive.  So here is my question.  The part number has a format such as

“XXXXXXXXXXXXX-##      ####X

Does any one know what the last five chararcters indicate?  I found a device whose part number matches mine except for the las 5 characters (####X). So i’m wondering if the last 5 characters have any significates?

Thanks

Mark

See if this helps  http://community.wd.com/t5/Off-Topic-Discussions/Bridge-Boards/td-p/353839 

Joe