McMurdo Station, USA

Got this in the mail the other day which is odd because I don't recall sending anything down to McMurdo this year. I did send one down to the South Pole Station though. Wonder if I got the address wrong. It pretty much looks just like the letter I got from McMurdo last year. Same IPY stamp. The cancel is a bit different though. I'm certain I didn't send anything to McMurdo this year.