An August 1993 doujinshi that I've just scanned.
It seems that, at the time, the circle's name was GG3 and Paradise City was only the title of this doujinshi.
But it seems that later Paradise City became the name of the circle and they've released many doujinshis, specially in the long running Tabeta Ki Ga Suru

http://www.doujinshi.org/book/339589/

Base +55