Apparently you can visually read magnetic stripes, if you can somehow see the magnetization patterns encoded on the stripe. I recently found out that this is indeed possible. The density is not that high and following methods will allow us to visualize the encoding.
In this video linked from the Hackaday article, they also tried it on various magnetic media like cassette tape (yes who remembers those?) and floppy disks:
Also related, here’s a teardown of the Coin Card, an electronic card that can emulate a set of pre-programmed magstripe cards on-the-fly. There are more teardown photos where this came from:
More Magnetic Stuff
I also posted about magnetic viewing films on Google+ earlier this year: