It's pretty neat. Not my cup of tea aesthetics wise though. I like them battleship grey or with some album toning.
I'm hoping to get more information about this one too.I've never seen one like it. Not silver. Reeded edge. Has the shield design of the seated half dime, not the half dollar...
Hmm. I don't have a half dime to compare it to, but it sure looks like a reasonable likeness of the genuine 1877 half dollar obverse I'm looking at. I'm guessing it's copper/bronze and die struck (die crack around ER on reverse, possible tool marks). I'd suspect it was plated at one time, and maybe ended up buried after someone figured out it was a fake.
It looks like brass to me, and you can see traces of the old plating. I would not be surprised if you're right about it having ended up buried for a while. Sometimes thin silver washes came off after long burial in the ground. I have dug many flat buttons from the late 1700s and early 1800s that were once silver or tin plated but lost most of their plating in the ground. Interestingly, though the thinner silver washes didn't survive the burial, I did dig a few 1830s buttons on one site that still had strands of the original thread through the shanks!