GEO Over-ride

From: "Traffick1" Joe,

As many now know, there is a way to do a geographic override by
country. (If you're in Canada and want to see US or UK or AU ads, you
would type the query into Google, briefly glance at the ads you're
seeing for your own geographic locale, and then go up to the address
bar and add &gl=us, or &gl=uk, or &gl=au, etc... this is great for
consultants and savvier advertisers who want to see who's advertising
in different parts of the world) When geographic targeting came out,
somebody had figured that you could do the same thing for it by
referring to the DMA "metropolitan area codes," but I forget the exact
sequence or whether you need to include multiple parameters. There
doesn't seem to be any info on it out there in public. I'm not sure if
Google really wants to spread the word on it. :) ... you can see how
this thing might get overused.
DMA Codes