What is it?

Found this today, not sure if it is civil war but the eagle looks old. it is brass or copper and seems to be filled on the back with cement or lead. Any info would help thanks.

It's a civil war period breast plate used by the US. It went on the cross belt for the cartridge box.  It is lead filled and had 2 iron loops that went through the cross belt. A strip of leather went through the loops on the breast plate to hold it onto the belt. A nice find. Worth about $70 to $90 in that shape

Great find, many of us dream about a find like that...... Definately a Union breast plate.

Thanks guys for the info. I am very excited now.