Yes, it's fibre for spinning, it's very fine (3 micron), antistatic, and conductive! It's stainless steel.
(see the seller's details in the image - it arrived from the USA much more quickly than I expected. Thanks Kate!)
Two surprises, I got my quantities muddled up - I was expecting 100g, this is 1oz which is about a third of that - and in the pictures it looked as if it had some colour but in fact it's metallic silver-grey just as you'd expect.
Alone it feels surprisingly fluffy but with a strange abrasive feel. I wonder what spinning the pure stuff would do to your fingers?
I had an idea about spinning it alone for pure stainless steel yarn, but given these things I'll try carding it with wool, maybe 1:2 or 1:1
Can't wait to see what the resulting metallic yarn looks like.