Field 515 is used to explain a situation that cannot be fully expressed in fields 362 and/or the 500 "Description based on" note. Examples:

Field 515 is also used for:

Report year or fiscal year coverage when the year does not end with December 31st and this fact is not evident from information given in other areas of the record

Suspensions of publication, when known. There is no limit to the number of years that constitute a suspension as long as the numbering is resumed

Serials issued in parts - when an issue of a serial appears in more than one physical volume

See also:

13.4. Numbering peculiarities notes (field 515)