I suspect they are claiming more ownership than they really have. Most of those records were made prior to 1976, back when copyright only applied if you made a copyright application. Seeburg didn't file copyright applications on them and they bear no copyright markings.
They just stamped "Property of Seeburg Music Library" on the disks themselves,
which were loaned out to customers but not always collected back.
Seeburg and its successors all went out of business decades ago, via court-ordered liquidation. The current "Seeburg 1000" site uses the name, but came along much later and does not seem to be a successor company. So these are now probably public-domain.
Their music was blah, but competently executed. Better than many modern low-end cover bands.
