Help With Coin ID

[Againstmywill]

I was to an older site, that likely contained homes at one point, that was being stripped of sod for a community garden. I was on speed 8 and it sounded like a machine gun with all the iron and bits of junk in the ground. I was able to find 2 wheats, one Army button, a Swiss Army knife and enough modern pennies that I don't have to worry about zinc deficiency any time soon. One of the items I found was a coin (I think) that looks Chinese or Japanese. If anyone has an idea, it would be very helpful. It is very thin and appears to be made of copper, as it is fairly bendable. There are no marks on the reverse. Park 1, 50 tones, mostly speed 7, and tracking on.