Dropping Dropped Ceilings

I'm going to slowly start doing the demo on the bedrooms so I can slowly get rid of the trash without getting overwhelmed. I'm starting with the ceiling. It's a 1 ft square tile system with a tongue and groove system that locks into the metal channels. So 4 trash bags of tiles later and a pile of tracks that I scrapped and the ceilings in the front bedrooms are gone....

and look what I found in the ceiling circa 1971....