This is Bronze 21's custom Feral Kid Boomerang. Here is what he had to say about it:
It's made of steel cut on a metal-blade bandsaw, then the edges were ground down using a 90 degree die-grinder, then buffed and polished, ending with a thick clearcoat to protect it from rusting. The next one will be polished aluminum. About $6.00 with found steel and purchased clearcoat.