Funny you should ask. Scientific data from the early dawn of home computers. Okay, so it was really the late 70s. Data that was recorded by an Apple ][, not an Apple ][+ or any other extension.
It was for my dad, stuff in the Physics world had churned and the ancient data (generated by a now dead post-doc) was of interest. So I called my friends with old gear. It was a several step manual process that involved several ancient Apples ][s, Proto-Macintosh systems, and finally an Macintosh laptop that had both a 3.5" drive and a USB stick.
I was much more successful than my dad thought I would be, his geeky son tends to be who he turns to when all others fail him, and he complains about not being able to do something with computers to my mom, and she makes him call me! :-)
The outcome has been somewhere between 3 and 7 published papers. All off of work that seemed to be dead end at the time.
It was sort of interesting seeing just how little space was taken up by the boxes of old Apple ][ disks when copied to a modern flash drive.