The Guide Star Catalog 2 (GSC2) is an all sky multi-wavelength, multi-epoch object catalog based on 1 arcsec resolution scans of photographic sky survey plates from the Palomar and UK Schmidt Telescopes.
Capability for unknown standard ivo://ivoa.net/std/openskynode.
The VO Registry may have more details; look for
IVOID
ivo://archive.stsci.edu/gsc23skynode.