It looks like a knock off of marcasite Jewelery. Marcasites were little single sided faceted hematite gems popular early to mid 1900's . Pitting and bend-ability indicates plated zinc alloy "pot metal"
A seam on the inside is typical of a 'gumball' ring-- one that comes from a gumball machine. Cheap toy ring. There was an article in the news a couple years ago that toy jewelry (among other things) was being recalled due to lead content (made in China), so think twice before giving it to a child.