original fitment type black steel washers

[mr mugello]

Do these have any corrosion protection against rust ?

[ToBoldlyGo]

I think it's referred to as japan'd. I think that was the general idea. But I'm not sure how successful it is. It's old school.

[missing lynx]

I think they are dipped in oil when hot this gives a blueish black finish I use to do this to tools in metal work at school but I can't remember why, Japaning is a black weather resistant paint finish