Mainspring
National Watch Company (Elgin) B.W. Raymond #829 Marked "Burt's Patent" "Mainspring Events" The large mainspring that serves as the power source for a mechanical watch movement can also become a.
National Watch Company (Elgin) B.W. Raymond #829 Marked "Burt's Patent" "Mainspring Events" The large mainspring that serves as the power source for a mechanical watch movement can also become a.