852 $f - Coded location qualifier:

Subfield $f contains a two- or three-character code that identifies the specific issues of the item that are housed in a location different from that of the main holdings of the same item. A two-character alphabetic code is composed of Qualifier type and Unit type codes; a three-character code is composed of Qualifier type, Number units, and Unit type coded. If the location qualifier cannot be expressed in coded form, it may be described in subfield $g (Non-coded location qualifier).

l, p Qualifier type

1-9 Number of units

m, w, y, e, i, s Unit type