Vintage hinged peacock pin
This pin is sterling with a gold overlay, with beautiful green and blue enamel. It is marked "Sterling" and "Siam" on the back. Siam is what Thailand used to be called prior to 1939, and again between 1945 and 1949, which would make the pin 63 years old at the very youngest. A unique feature is that the tail is hinged, so it can be lowered to be positioned at a 90 degree angle from the body. Worn on the shoulder that way, it would appear that the peacock's tail is spread behind it.
This pin's hinged tail makes it a unique piece, although I don't think it's particularly rare. I have seen the same and similar peacock pins for sale. In fact there is currently one being offered on Ebay! Authentic pins like this are being sold for up to about $100. Considering my father paid $3 for it, that's a pretty good investment in a colorful and interesting vintage piece.