Mr. Winkler told me this in an email.
"Thank you for your order. The RnD Hawks are all made in 5160 steel. Since they are primarily made for combat I use the grade that has a little better edge holding. There is still plenty of shock resistance for breeching. I am probably going to change from S7 to H13 for my breeching and crash axes. I have some test pieces in process that will determine if I change or not. To get a RnD Hawk made from this material would delay your order several months and personally I don’t think the change in material for this design would be warranted. The cost difference is negligible. Frequently people think because 5160 is not one of the new glamorous steels it is lacking in today’s market. I have tested several steels including 5160, A2, S7, D2, cpm154, cpm3v, 52-100 and soon
H13. For axes by far the 5160 has proven to be the best except when regularly cutting metal, concrete and cinder blocks. In those cases trading off edge holding for shock resistance is acceptable."
So I went with the 5160, and here's a pic I stole from the Internet, somewhere. I'm getting the same on mine, black micarta with black KG guncoat...