The so-called "purple passion" glue was used mostly in 1975 models as well as a few early 1976 models. Fletchair has the list by s/n of aircraft in which it was used. Some aircraft only had it used in part of the plane (e.g., tail but not wings) -- Fletchair can tell you which. The remedy for any delamination noted during inspection is repair with Service Kit 125A in accordance with Service Bulletin 155. That said, there are a lot of purple glue airplanes which haven't experienced any delamination in the 37 years since they were built. If you're buying one of the affected airplanes, proper inspection per the SB should identify any problems, and it's not hard to fix.