Field 851 was made obsolete in 1993.  Both indicator positions were undefined.  The subfield codes were:  $a (Name (custodian or owner)), $b (Institutional division), $c (Street address), $d (Country), $e (Location of units), $f (Item number), $g (Repository location code), $3 (Materials specified) and $6 (Linkage).  Location information may be contained in holdings/bibliographic field 852 (Location).