The vast majority of library music 78s are regretfully undocumented. Many don’t have pictures online with large gaps in cataloging sites. Let alone matching the music to the titles which may have changed if they were reissued.
Late era library 78s generally have a different style of music than the relatively more famous 60s and 70s library albums.
They are uncommon in the sense they are often overlooked. Piecing them out for sale is also much more difficult than getting rid of them all at once. But they would be a great help to fill in gaps and piece together those library music CDs featuring “archival recordings”.