Unused vintage item.
These jumpers were unsold stock from the early 1960s or thereabouts.
They still have their original Chemstrand/Acrilan tags (though these tags have become rather creased over the years, as you can see).
They have been properly stored, so they have survived very well for several decades, and are perfectly fit to wear.
However, in view of their age, they should be hand-washed before use, and treated gently.