Hi; I concur with Ahab8; It it a Ball Button circa 1810's / 1820's. Some call them BlowHole buttons ok. Although that is not an accurate term for it the term seves as a General Purpose Id source ok. They can Date all the way back to the 1600's. Nice Find. I believe the locket cse there Dates to 1850 - 1880's ok. PEACE:RONB
PS: Please remember to ALWAYS show both sides of any object and the Shank when it coomes to buttons. We can tell the age by the style of the Shank ok. PEACE:RONB