Old (big) mag cards?

[John Ioannidis]

a related problem is how to read old magnetic media when you don't have the original equipment, or when you don't trust the integrity of the medium and its ability to go through the reader mechanism, a common problem with very old magnetic tapes that have been stored in less-than-ideal conditions. Search for "magnetic developer" in your favorite search engine. I still have some Sprague magnetic developer that came in little pressurized spray cans *somewhere*. If/when I find them, I'll "develop" an HP-67 card and post the results.