I think,it dates to the Mexican American War.A friend dug the near exact hat pin.He also dug a breast plate that features that same motif,that strongly resembles at least two bel buckles of the same period.Yours is of Mexican origin and is likely authentic silver.The story in my mind is likely a veteran of that war,went to Your Gold Rush,carrying his souvenier of his days in Battle
Crusader brings up a great point in that normally the snake is in the Eagles Beak,but I have never seen a snake type buckle like this if it is(sure looks like the British Snake buckles)to allow it to function in that capacity it almost couldnt be in his beak?
I am torn now,it may be American,pretty sure it dates to the 1830-40's