Some years ago I received a card from Chile but at the time didn't notice the stamp which I came across just the other day. It commemorates the 50th anniversary of the Treaty of the Antarctic 1959.
The postcard above shows the way the Antarctic is divided up with the Chilean claim being to the left. I have another very similar one of the Arctic region.
I've previously posted two other Antarctic stamps, one from Port Lockroy and the other from Monaco.
This is a post for Sunday Stamps, now hosted by Violet Sky at "See it on a Postcard!"