It is what's called a completer pin. I found it on ebay and my wife bought it for me cause she is the best. Plus she is jealous of my Donalds but won't admit it.
Definitely show me the pin when you get a chance. I don't think I have it yet, so I'd like to see what it looks like.
You should get all Donald pins. I am just biased like that. I encourage everyone to get only 1 character because it makes the trading and hunting for pins much more fun. When I run into a wall with Donald and can't find anymore I will start my Chip and Dale collection until I come across any Donald one I do not have.