Some really stiff wire going to I presume selenium rectifiers...

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I thought it was bare copper wire and rigidly shaped to avoid contact and shorting out etc..

But (and maybe it's heavy oxidation or tarnish?) but there is no continuity at two outside points on this stuff
 

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However if I touch the probes on the soldered on eyelet terminals I get continuity 

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This IS an old boat 🚢⛵ anchor ⚓ so do you think it's just oxidation?

Ok maybe bust out some sand paper and retry

Ok nm I scratched it up with a $5 buck 110 and got continuity
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Man that's ridiculous

That solid copper wire is varnished with an insulating varnish, you can tell by the orange colour it has for starters.

Varnished copper wire is used to wind transformers and electric motors among other things, if it was not insulated that way a transformer or motor would just short out in the windings.
If it was insulated with a plastic sheath it would become too thick to wind.

It is also common practice to dip a wound transformer into more varnish to prevent them vibrating and making a 50 or 60Hz hum.

Just look at your variac and imagine the shorted out windings if there was no varnish on the wrie, usually the area on a variac where the viper brushes over for the mid output has been sanded down so the viper can touch a bare area of the windings.

*Enamelled* wire.

Ends were scrapped/scratched for soldering.

*Some* modern wires (which I hate) use a fancy so called "self soldering" enamel (poorly chosen name, if anything it should be called self stripping) which insulates at normal temperature but EVAPORATES LEAVING NO RESIDUE BEHIND but shiny copper instead at very low 130C temperature.
For reference 100C is boiling water, 183C is molten solder, so you save time and effort by wrapping unpeeled wire around a terminal and just applying soldering iron, it will self strip.

You save a few seconds per soldered joint ($$$$$$) BUT it is very weak.

Acceptable in CHEAP wall warts made by the millios for peanuts, it has NO BUSINESS inside a Tube amp PT or OT, yet I find that crap everywhere.

I have rewound Marshall and Mesa Boogie transformers originally wound with that crap.

What were they thinking?

Thank you for the responses that was very educational (and entertaining) 

That varnish seems to be good stuff as far as insulating properties 

Unfortunately it is greatly hindering my meager feeble attempts at seeing if these selenium rectifiers are working because idk if they are not working or I'm just not not getting conductivity 

Also there is a curious looking potentiometer/rheostat device.  It almost looks like it has windings like a variac autotransformer but its diameter is only about the size of a silver 🪙 dollar 

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It was on the front panel of the box with the knob missing I guess to control voltage

That´s nothing more (or less) than a Macho Man potentiometer, called a Rheostat.

You are seeing the wirewound track, embedded in ceramic material.

Construction and operation is exact same as in a carbon potentiometer, only way higher dissipation.

Unsolder top and center wires and measure track resistance end to end ... unless it is printed somewhere.

YOU are THE macho man amigo 

Gracias 

If you are interested in the device here is the front panel
Oh yeah the knob for that rheostat is just to the left of the "79" and the bottom middle is a big green lense with a bulb 💡 inside

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The lid pops up as well as the chassis slides out

There was no transformer  just mains to selenium rectifiers 

Then there were a couple humongous capacitaters and a one thousand pound choke

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You always bring intriguing old stuff to the table

Now WHAT is that?

Remember to measure rheostat value.

Idk sir

Can only speculate many moons ago a student or hobbyist built a peligroso DC power supply?

CUIDADO !