(YZ, Yale Zone Catalogs, Yale Photographic Catalogs, Yale Catalogs)
(mid-20th century catalogs totaling 400,000 stars)
The name Yale Observatory Zone Catalogs is used for a series of
starcatalog publications by Yale Observatory
from 1934 to 1983, which have been combined into a database of
400,000 stars.
The zones were declination-ranges: I'm not sure if they covered
the entire celestial sphere, but they covered the vast majority
of both hemispheres.
Names for the catalog in use during their development
include Yale Zone Catalogs, Yale Photographic Catalogs,
and just Yale Catalogs.