What is this?

[Fred Cisin]

On Fri, 10 May 2019, Chuck Guzis via cctalk wrote:
> Found a bit more detail on WALNUT:
> https://nvlpubs.nist.gov/nistpubs/Legacy/TN/nbstechnicalnote157.pdf
> See page 86.   Includes some B&W photos, including one of the unit that
> you show.
> Was WALNUT ever used outside of the CIA?

With no first-hand knowledge, I would assume that NSA also used such.

Half a century ago, when I worked at The National Space Science Data 
Center (NASA, Greenbelt) we dealt with a lot of data.  But that is like a 
floppy compared to NSA, especially the Utah Data Center!