That is an interesting piece, I think those grooves make the blade more spring like and help prevent the blade from cracking, not sure just a guess. Boy the torque on the tip from a swing would land an extremely high pounds per square inch impalement. I can see how a very thin quick handling spiked like sickle would be very deadly considering body armor of weaved fiber and beads. Pair this up against a spiked tomahawk and this has more reach with an edge inside. Ouch!
I like contrasting this to a straight blade sword and tomahawk, too bad I can see this type weapon and techniques used in spar. Its deffinatly different.
Aaron