They were made by both Hagstrom and (under licence) by a Czechoslovak firm that just called itself Futurama. The Swedish models had nicer design touches (like the cheese-grater grille) and a rather nicer neck.
In good nick they play as well (or as badly) as any other 60s shortscale. The intonation is clumsy but with flats and a thuddy sound that's no more of a problem than it was for the Hofner Violin, its exact contemporary.
If you run out of trussrod adjustment and the neck is banana'd then the very high action which results will leave very inconsistent tuning up and down the neck.