My vinyl album of Alchemy states on the back cover "This is a recording of excerpts from one Dire Straits performance. As it contains no re-recordings or overdubs of any kind there are occasional stage buzzes".
It has been a moot point for many years as to whether it encompassed both nights or just the one. I prefer to live in musical heaven/bliss/ignorance and think of it as the one, with no corrections or external interference - don't i just love those 'occasional stage buzzes' :-)