This is a Word War I German patriotic bracelet.
It is made of a brought back grenade shell and altered by a jeweler into a typical period bracelet for wearing by a girlfriend or wife of a German soldier.
On top is affixed a small enameled 1914 dated Iron Cross, which is flanked on both sides a by a silver colored small branch with leafes.
For putting the bracelet on the wrist one should push the pushbutton to open it. There is also a small safety chain for preventing loss in case the bracelet would open unexpectedly.
Simply a great period item with a lot of history!