Technical flathead head bolt/stud/nut washers

I have read to make sure to use hardened washers under the head bolts especially with aftermarket aluminum heads.
Are the washers that the old Ford parts stores sell hardened, stainless, chrome?
I want something that will look good on a polished head...

 

I got mine from Gary ("GOSFAST") on the Ford Barn. I seem to remember they are made by ARP. I believe that they are pretty generic, and the washers they sell for small block Fords and Chevy's will work on a flathead, as long as they are hardened and 7/16". They have a chamfer on the inside diameter that is installed towards the head of the bolt.

 

Don’t know about hardened, but washers for my big inch flathead are COPPER and I got them thru O ‘Reilly’s and have retorqued Head bolts only 3 times and they are holding torque,so I guess they are hardened? Flatheads Forever!

 

SBC washers are 7/16 and work well. ARP, and many others.