I believe this is circa 1930's-40's. It is not signed and done in pot metal. It is a large, impressive pin. The USA flag has blue rhinestone "stars" and flat back red and clear baguette rhinestone "stripes". Amazingly, it appears to be all its original rhinestones! A few of the clear ones have some dark spots, but overall excellent condition for such an old piece. The pot metal has a dark, aged patina.
At first I thought there must have been something else connected to the chain, but in doing research, I think it is supposed to be that way.
It measures 2.5 x 2 inches.