This is accurate. McConnell's in England (who took over Rattray's production in the late 1970s, I believe) closed down in the late 1980s/early 1990s and K&K then took over their entire portfolio.I‘ve read that K&K took over production around 1990.
I've smoked tons of Rattray's from all three periods and it's all excellent! I love the stuff I have from 2000-2010 (when Arango took over distribution from XYZ) and it's perfect right now, IMO. Of course the stuff from the 70s and 80s ain't bad...