ATR Magnetics has only been in business since 1996, so these are not vintage tapes.
These are dupes of some kind. If they are dupes of master tapes, they'd have value to many collectors. As long as you kept the sale on the QT (the label can block the sale), you could probably get some good money for them. That said, you'd have to play these tapes to find out if they're duplicates of the session masters and not simply someone's dubs of an LP or CD release.
I am not sure how much music can fit on each tape. There appear to be two reels for each title, so I'd imagine that there's more music than a simple LP dub, but again, I don't know this medium.
The tapes themselves have no info on the provenance.