The Data Lab hosts both USNO A2 and B1 as astrometric reference datasets. For description of these catalogs, see:

The usno.a2 table and usno.b1 table have been crossmatched against our default reference datasets within a 1.5 arcsec radius, nearest neighbor only. These tables will appear with x1p5 in their name in our table browser. Example: usno.x1p5__a2__gaia_dr3__gaia_source.