Harvesting a line cord for a widowmaker test setup revealed its inner secret:
The conductors are as thin as I’ve ever seen in an AC line cord, with 0.5 mm² = just under 20 AWG. The color code doesn’t match USA-ian standards, but neither does the labeling, so I’m not surprised.
If the individual strands seem unnaturally straight, they are, because they’re made of (presumably) copper plated on a (presumably) metallic core. Here’s what they look like after bending them sharply around my fingernail:
Wonderfully springy, utterly non-magnetic, and surprisingly durable.
Scraping the 0.02 mm strands with a sharp blade reveals a silvery interior, so it’s (presumably) not copper-coated plastic. Aluminum springs (ahem) to mind, but I’d expect tiny aluminum strands would snap (or at least deform) when bent and erode quickly when scraped.
Each wire measures about 1 Ω / m from the plug (a convenient 40 inch = 1 m away), which is the resistance you’d get from a single hair-fine 5 mil = 0.13 mm strand of 35 AWG solid copper. An 18 AWG aluminum wire would have the same resistance as a 20 AWG copper wire, both of which should be 32 mΩ / m: a factor of 30 less than this crap.
I have no idea what low-end Chinese factories use in place of copper, but it’s gotta be really cheap.
A hank of the wire goes into the Box o’ Springs, in the event I ever need a tiny straight spring rod; you definitely can’t wind this stuff into a coil! It might be fine enough for a crosshair / reticle, at least for crude optics.
The Smell of Molten Projects in the Morning 
Must be copper clad steel?
Wait – – you said it was not magnetic. Stainless?
We now live in a world where reprocessing something like stainless steel scrap into wire, plating it with a copperlike substance, then lying about the result is … cheaper than using copper.
Perhaps slag mixed with recycled waste, processed by Uyghur workers? Another Chinesium grade quality product.
I must fire up the Geiger counter!