If you don't think the Post Office is stupid.

I had to do a double take on this myself. I went to search for a zip code for a particular address. So I went to the zip code finder that the United States Post Office has set up. Among the pieces of information they ask for, in order to locate the proper zip code for that address is the zip code. Of course if you knew the zip code in question you wouldn't need to use the zip code finder.