It's an acetate from 1979... Very rare, I was expecting a high price, maybe not that high, but...
These acetates are a beautiful item to collect.
Does they sound any different from the studio recording though?
Most of them are the same version, used to check levels of sound before release it or as radio previews. Some of them are really rare as include early versions pressed to listen to them at home or the hotel during recording process. Sometimes they even are unreleased songs. Obviously these last are VERY expensive and rare.