here's something you've never seen, and will likely never see again -- a prototype floppy disk drive. this is the ill-fated IBM DemiDiskette. it's not 5.25" nor 3.5", it is 4 inches! 
here's what the disk looks like compared with a 3.5" floppy.
very much a prototype, check out the wire-wrap job!
bottom of the drive indicates it was prototype #5. on the left you can see a little bit of the unusual head stepper spiral cam mechanism.
it came with this aluminum blank loaded in the drive.
dates on some of the paperwork go back to just about 38 years ago today!
IBM engineers designed it to be a very low cost (<$100) floppy drive using low cost media without sacrificing reliability. unfortunately, due to internal politics, the drive was late to market and ended up costing several hundred dollars.
it ended up losing to cheaper 3.5" drives from Sony.
this is what it looked like when it hit the market.
i gave one of the prototype diskettes to @foone, natch
