Cr-V. Steel (#8660) with harden & Satin Finish
It can be worked with 1/2"Dr. Ratchet handle & 17 mm Spanner
12-1/2" Dr. Sq (F.) Hex shank Bits
6-Star (TX) + Tamper: T-55~T-100.
6-Spline + Tamper: M10~M20