The first microwaves were actually called a radar range AND they were so heavy it was crazy!!
I bought my first one at JC Penney in 1980. It was still working in 2000 !
“they were so heavy it was crazy!!”
They were lined with lead...
Now they claim we don’t need the lead lining? They say the holes are too small for the waves to escape through. I would feel safer with the lead. :)