We have a faux pearl/shell sweater clip / guard vintage item.  It measures about 8 1/2" in L with the clips about 1" across the center.  There are shells and faux pearls on the end rounds over the clip - 1 side the large shell is broken as shown in my photo's.  The center chain may not be the original chain as the back side of the rounds has a more gold tone and the chain a silver tone.

Sweater Clip Guard Vintage