WWII was the latest development of the wire recorder which Dad used for recording for audio visual advertising. and also "Tinsel" which was the original "Mylar" electrplated/ vapor deposited with chrome. War surplus Tinsel was sometimes available to 3M employees. We saved it for every year's Christmas tree. 3M developers made Mylar recording tape possible. "Webcore" made some of the first tape recorders.
Just my memories YMMV
geezer