Silver:
  You and Cabelas are correct but without an end view or the opened breech, with the Kersten double extensions, typical O/U forend and the pipe style frame reinforcements, it has all the hallmarks of an O/U.  It does look to have a Funk style safety and top tang shot and ball selector.  Somethings amiss though.  There's a multi-piece forend on the left side and I can't tell on the right side.  Also me thinks that they've mounted the scope in reverse???  I thought it might have had a tube insert.  Kersten designed the extensions for SxSs and I don't think many SxSs or drillings were made with the Kersten lockup post 1900. 
Kind Regards,
Raimey
rse