I suspect that the manufacturer or LP records sellers in the 60s or earlier sealed some records into inner plastic bags in order to conceal their defects (warps or mold spots, which is the case here). A year ago I came across an LP by Miles Davis (not KOB, a later title) with sealed inner bag. I was about to purchase it - the outer jacket was opened but the record itself was sealed as described).
I didn't purchase it then, but later on, the seller opened it and the record was warped and that warp could not be cured by a vinyl flattening machine.
I didn't purchase it then, but later on, the seller opened it and the record was warped and that warp could not be cured by a vinyl flattening machine.