Fossil? Coin? Sun/moon? Pendant?

[Baggflo]

I need help friends. A buddy of mine posted a pic of this on FB asking for help identifying it, no one could help. I loved it so I offered to buy it (which I did). This is all the information he could give me.

My buddy's uncle died and left him a metal briefcase full of mostly old coins and a few other valuables. He lived in eastern Massachusetts. Items included really old papers, antique watches, coins as far back as the late 1800's and that thing. One interesting item was a fuel ration card from WWII...

The intriguing part to me is how defined it is - it must be man made, right? Its about the size of a large coin or small pendant - I'm not even sure it's fossilized, it just looks that way to me. Your help identifying this would be greatly appreciated.

[Al Dente]

It looks like a small concretion to me. Here are some more from Google: https://www.google.com/search?q=flat+concretion&source=lnms&tbm=isch&sa=X&ei=5-pfUv7MGcH22gW4pICYDQ&ved=0CAcQ_AUoAQ&biw=1126&bih=786

If you scroll through these pictures you will see some similar ones.

[Fossildude19]

I agree. Concretion.

Regards,

[Baggflo]

Thank you guys, your links sure indicate you are right, I saw some similar ones in the photos. Thanks again.

[Herb]

it would make cool pendant though