Actually, the entire thing is brass. the light just reflects funny, and makes it look brighter.
I use 3 or 4 different endmills, depending on the detail I need to produce.
1st Rough Pass is a .125 2-flute carbide endmill. I use that to remove all the extra material around the geometry.
2nd Rough pass is a .062 2-flute carbide endmill. I use that to rough out the gross features in the geometry, to save the life of the next tool.
1st finish pass is a engraving tool with a 20 degree taper. the tip is .005 I use that for most of the features in the geometry.
2nd finish pass is a engraving tool with a 20 degree taper. the tip is .003 I use that to get the tiny details like the R in the corner.
The geometry on all my dies is 4mm deep, thus the need for a good roughing pass. The whole die is 3" by 3".
I make the mounting holes using the .125 tool, after everything else is done.
The counterbores on the mounting holes are done by cheating: I have a counterbore tool in my drill press. It’s takes a few seconds compared to 10 minutes on the cnc.