most anvils are probably in the 48rc to 54rc range, generally they are a bit softer than hammers. Hardie tools hardness depends on what the use of the tool is. Some I make out of mild steel others I make out of 4140, H-13 or S7. I even use some leaf and coil springs to make tools.
I make most of my hardy tools from coil springs. I have a biiiiig coil spring from the rail road. the stock is 1 3/4" diameter and the coils are about 12" across. To make a hot cut I use 4" for the whole thing. The finished hot cut is about 4" tall, the tang is about 4" and the hot cut is about 3" wide. I harden in peanut oil and then temper in a convection oven to 500 degrees. See my post "My blades cut Steel" MY BLADES CUT STEEL