I'm with GA. It always read incorrectly, to me, to leave out the "of." It doesn't seem to be regional to me.
One regional difference in America that blows me away is when we speak of numbered roads such as interstate highways. It does appear regional to say "I'm driving on the 5" versus "I'm driving on 5." I don't know all the linguistic borders these apply to but we use "the" commonly in southern California but not in northern California. I polled enough people that I consider this observed difference to be reasonably true (I used to live near SF, now near LA). No idea where it comes from.
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