Here’s a weird bit of dead media: a Smith-Corona audio-letter that used a “Letterpack cartridge” (which appears to be a 3.5″ floppy disc) to record and play back personal voice-letters sent by post. The apparatus is a fascinating dead branch in design history, something that looks like it might be descended from a desktop intercom box, and distinctly unrelated to the apparatus we put up to our faces and heads in this era.
This can really be seen as an arbitrage point between high long distance tariffs by monopoly telco operators and a willingness to tolerate delays in personal voice communications.