I recently purchased a big box of very old reel to reel tapes of varying sizes, and inside the box were about a dozen three inch reels, all of which had been mailed, way back when. The address labels showed the "from" being the name of a Lieutenant Colonel, and the "to" being a similarly named person in New Jersey. (I have deleted the last names and street name, from the scan of the tape box, in order to keep the identity of these people private.)
What these tapes contain are audio letters from an Army doctor to his wife. The two I've listened to so far, each just under 20 minutes long, date from July, 1954, while the doctor was stationed at the 121 Evacuation Hospital in Korea.
Rather than go into any detail or play up or down any particular aspect of these tapes, I'll just let them speak for themselves. If there is interest, there are several more of these tapes, as yet unheard by me, that I can share here in the future.