Hi. I want to amplify this.
"SOUND FILMSTRIP IS AN AT-RISK MEDIA FORMAT. I am the only person on earth preserving American filmstrips. The media format is largely forgotten and very endangered."
True or not, it *feels* true.
I've been searching on again off again for years for particular items with no luck. It is as if they never existed.
Various libraries seem to have dumped their catalogs into a pit or something. Vanished overnight.