This is taken from a soundcheck at one of the Japanese shows in August 1986. His voice was still good there.
There was a radio interview with Obie around the release of the 2010 special editions where he talked at great lengths about a new technique that had allowed him to restore tapes that were damaged by floodings and this having been one of them. Of course he didn't say which show it was, other than it being from a soundcheck in 1986.