Old (really old) hard disk platter?--The Ruggeduino: compatible with Arduino UNO, 24V operation, all I/O's fused and protected
It's a hard disk data platter from a very old school disk drive, circa minicomputer and mainframe era. Read/write heads would be positioned over the proper track and the data would be read or written to it. Ones I worked on had ten such disk platters stacked on a single spindle. Spare platter cartridge would cost around $1K so making backups was not a cheap operation. Lefty
That platter actually looks like something from one of these:http://en.wikipedia.org/wiki/IBM_305_RAMACThen again, most of those platters from that time look the same...Now if you want to see a real treat, check out the Bryant Model-2 Series 4000 from 1965:http://archive.computerhistory.org/resources/text/Bryant/Bryant.Model2.1965.102646212.pdfThat must've been one heckuva machine to see running!!!
I had to "tune" the printer every couple of weeks. Adjust the 132 set-screws behind the hammers so that they hit exactly when the desired character was in front of the hammer. I would print whole lines of dashes and it made a terrible racket. I should have been using ear protection. Eh??
I had the reel to reel in my yard looking like an old washing machine - a high tech redneck - yeeee hawww.