Please have a look at this (I'm speaking about Coldplay's first release.)
"All I can say is that he bought it in Piccadilly records in Manchester a long time ago (1998) before they became very famous. At this time he was living in England and used to go once a week to that store.
The next sentence can be either
"500 copies had been released not 50"
"500 copies were released not 50".
Which solution is the best?
I think the first one, past perfect, is the best because first the record was released then he bought it, but it seems evident that you can't buy a record before it is released so past simple might fit too.