The king of desks : Wooton’s patent secretary / by Betty Lawson Walters. (OCLC #49110)

MARC field 019 is used in OCLC for OCLC Control Number Cross-Reference; that is, when two (or more) OCLC records are merged, one OCLC accession number is kept for the record, and the others are put into 019, each into its own ǂa like:

019 __ ǂa 253458412

Records can be merged when a duplicate is accidentally created, such as when a master record is not found for some reason, or when the cataloger did not realize that the differences between descriptions are not sufficient to justify a new record. They can also be merged when cataloging rules change; for example, many older ebook records have 019 fields from when the title was cataloged on multiple records (each specific to one vendor/aggregator), and have since been combined into one provider-neutral record.