I had another success trading my shields for old computer stuff! Here is one question for you: one friend sent me this item.
What is it?
Here's the blog post soliciting for more computer stuff. All my shields are up for trade:
Old (really old) hard disk platter?
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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
RuggedCircuits:
Old (really old) hard disk platter?--
The Ruggeduino: compatible with Arduino UNO, 24V operation, all I/O's fused and protected
Correct! Did you peek at the file name for hints?!
retrolefty:
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
Wow, that was good background on this type of things. The donor did mention it came out of an ancient large hard disk drive. Nowadays we don't distinguish among hard disk, hard drive or hard disk drive and I just realized how ridiculous it is (with silly me included for the last 20 years). The hard disk is this platter pictured above, and the drive is like a washing machine!!! (hint, I don't want the washing machine) It's like calling the desktop computer case the CPU, while the real CPU is the processor that sits inside of the case. I'm sure if I lived to 250 years old I would hear this type of mistakes a lot. 
That platter actually looks like something from one of these:
Then 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:
That must've been one heckuva machine to see running!!!
Need to get a large optical drive now ...
cr0sh:
That platter actually looks like something from one of these:Then 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.pdf
That must've been one heckuva machine to see running!!!
I wish. Mine is 14 inch in diameter. I think it is from a much later model.
Wonderful story. I'll have to read up on hard drives. I've collected a small stack of 3.5" hard drives some years ago starting from maybe 200MB. Again I don't have space for any major-sized stuff 
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??
Worked as a field engineer for mini-computer systems in the 70s and I too had to support those massive 132 column drum line printers. Performing that hammer alignment procedure was one of the most time consuming jobs there was to be performed, but had to be done from time to time or else the lines would come out all wavy and look really bad.
To get an idea of how expensive those fanfold 132 column line printers were in the 70s, the common one I worked on cost the same as my California typical 3 bedroom suburban house at the time!
Lefty
As late as the 1990s we had huge hard drives like that at a company I worked for. The first mainframe I worked on (HP) got replaced and they told me if I could lug it out, I could have it. The huge platter based hard drives made great end tables that said EMC (squared) on them. I had the reel to reel in my yard looking like an old washing machine - a high tech redneck - yeeee hawww.
Thanks for the ride down memory lane with those platter shots.
I had the reel to reel in my yard looking like an old washing machine - a high tech redneck - yeeee hawww.
LOL, you know your a high tech redneck if you mow your lawn and find a tape deck!
Lefty
I remember using an HKC8800 compute in the 80's, an Apple clone with a main unit like a thick keyboard and an optional driver bay with two 360K floppy drives. I just couldn't find any info on Google. Played many games on it as a kid.
OP: I've got a spare platter in my cellar. And one whole disk (eight platters). The one I have held 300Mb. At the time I used this we stored images (Wow - you f*ing stored pictures on these - awsome!) from a scanner. A standard scanner we made was thr size of a big car and cost about two/three houses. The disk drive was about half a house, each disk a mere twentieth of that.
Ah yes, those were the days ...
A story went at the time, that "a person" had used a discarded single platter on the 2nd floor to prop up a window to get fresh air. A gust of wind dislodged the platter wich fell vertically down and sliced a clean "coin slot" in the roof of a parked car below. (Considering the size, weight and strength of all materials involved, I find the story believable)
That's not a 'big' platter. Big platters were about 4 foot in diameter. I've seen some here http://www.tnmoc.org/large-systems.aspx