Creepy and beautiful at the same time. 
For some reason, old tech stuff like that always attracted me.
@dchomak
They look like capacitors, also known as condensers to me.
With some nice screwing terminals. Maybe they were used as start/rum capacitors for some kind of motor (or generator)?
They look like Mallory electrolytic capacitors.
Filter caps for power supplies in vacuum tube amps?
Cheap because they were not needed for solid state devices?
I'm thinking the 1971 date is tied to computers somehow.
-Garry
If I was in an underground cave I would rather have 30 lumens of warm high CRI light. I can understand the resistance to upgrading if you have gear that is well known (and well known flaws) vs. new stuff that needs testing and familiarising, and training others on use (health and safety).
The suspense is killing me. Someone guess this correctly now darn it.
I would guess some type of capacitor, but the sleeping with it under your pillow the first night thing is throwing me off. I can't imaging wanting to have a capacitor anywhere near my rock filled head. I wasn't playing with electronics much back then. So I have no appreciation for the shortage of this type of part.
I wasn't even born yet in 1971!
-Garry
I remember my much older sister telling me that until one goes deep down into the earth, they have NEVER seen darkness. Only then can you experience the total absence of light.
Another coincidence! Only last night I read this article. Huge Dark Matter Experiment Finds Nothing but More Mysteries | WIRED
How’s that for a LUX meter………and it’s buried in a cave.
It looks like a chassis mount capacitor, the kind used in output stage of power amps. Maybe you could get them cheaply because of transistor amps becoming more popular?
But you all have not answered every question. I am also hoping that someone will give us more than I am asking, stuff I didn’t know.
You nailed the manufacturer part of it! Here is another pic
There are a lot of reasons why they are no longer as necessary. What are they?
Computers, interesting idea.
But What happened in 1971?
Maybe a company switched from linear regulated PSUs to SMPS, rendering their stock of big caps useless?
Could be at that time.
Oh the suspense. 
Rated at 40 VDC they certainly are not for vacuum tube power supplies. Filter caps for B+ power supplies would be 470 volts or so.
I remember that in 1971 the HP hard disk drives that I worked on had big capacitors like that for emergency head retract in the event of power failure.
Back in the day, often times Amplifier manufacturers would would use huge non-polarized capacitors to protect the speakers from any DC current. Theoretically that would impact low end response. In my opinion the better designs wouldn’t need them. 2 of these in series in reverse polarity could mimic a non polarized capacitor. When that was done though, shunt resistors of the proper value had to be used. It was a kludge. My personal use was for filter capacitors in power supplies.
But around that time” things were a changin………………”
You are all going to figure it all out… and more…… I want to learn more too!
I have taken too a long a lunch break. I’ll be back later, until then I will leave you with a quote I just came across.
“Resistance is futile, but capacitance has potential”
Aluminum electrolytic capacitors with excellent initial electrical performance, voltage combinations, high current filtering, energy storage, and good ripple capability. High performance, high capacitance and high CV rated. The were/are used for spot welding, DC/DC converters of +500W power, DC/AC AC/AC +500W converters, motor starters, flashtube ignitors, audio crossovers, frequency converters, DC links, DC buffering, UPS buffering ….
How did you get such a good deal on them?
They are so big. Were they used in some kind of computer?
Hmm . . . in 1971 Intel released it's first microprocessor. Is this related? Death of main frames or something? I'm probably stuck on 1971, but the "event" could have happened earlier.
-Garry
Me too! I love learning about older technologies.
Hmm . . .
-Garry
Did the introduction of super-capacitors cause a temporary drop in traditional capacitor prices? Is that how you came to having a one night stand with one of those caps?