Armor Steel in quenched and tempered armored heat treated steel plate.
MIL-A-23560 heat treated plate made for good ballistic resistance.
MIL-DTL-46177 heat treated plate has higher hardness than MIL-A-12560 with thickness up to .250" thick.
MIL-DTL-46100 heat treated plate provides excellent resistance to penetration with thickness up to 2" thick.