Wire scrap help

[Onions]

Question for you wire scrappers out there.

I am not an active scrapper, but do save anything I happen to bump into if it has value.

I recently came across a decent amount of some old wire from a farmhouse remodel I was working at. I got the owners blessing to take it and noticed that it is unlike any other wire I've stripped. It has a fabric-like sheathing that has gotten quite brittle and mostly crumbles off the wire. Here is what concerns me: It is certainly copper, but there seems to be a thin layer of discolored metal coating the copper center. Its super thin and it easily scratches through to shiny copper. Any idea what I am looking at here? DId they do this sort of thing back in the day (early 1900's) or is the copper just reacting to the sheathing and causing this discoloration?

If this is, in fact, a different metal coating the copper; would this cause the scrap yard to categorize my entire bucket as a lower grade copper?

Maybe a stupid question, but I've never seen it.

[linkster]

Its just old copper knob and tube wire. I would probably use a respirator or a dust mask when stripping it as it could/probably have asvestos in that insulation. they should gove you no 1 price for it cause it is all copper. you could take a piece of sandpaper or emeroy cloth and shine it up if they give you trouble no 2 prices

[messymessy]

The wire is coated and can be put in with your #2 copper. I believe it is a tin coating.

[coppers4me]

Have stripped this kind of wire also, and concur with linkster both about the mask and the fact you should get #1 price,Unless you burn the coating off.Then you will get #2 price. Hope this helps