Nova Treasure is correct, it is a New York (State Militia) button, dating from the 1850s-1860s.
But the emblem on it is actually not the New York State Seal. See info with button NY-30 in the Albert button-book. Also, see the top of page 197 to view the actual New York State Seal ...which shows two standing female figures, one on each side of a very large shield, and the shield is not "quartered" with four separate smaller emblems.